1
CHE-310 Organic Chemistry I
Instructor:
Office:
Phone:
Office Hours:
e-mail:
1.
Dr. James L. Lyle
NSM-D-323
(310) 243-3388; 243-3376
Will be announced in class; open door policy
jlyle@csudh.edu
Grading:
Daily exams
4 exams @ 100 pts
final exam
homework
=
100
=
400
=
100
required
600
Letter grades will be assigned on the following basis. Grades are
not curved.
A = 100-93%, A- = 92-90%, B+ = 89-87%, B = 86-83%, B- = 82-80%,
C+ = 79-77%, C = 76-73%, C- = 72-70%, D+ = 69-67%, D = 66-60%,
F = 59-0%
2.
Required Texts:
Organic Chemistry, 6th Ed., Morrison & Boyd.
Study Guide for ...
Molecular Model Kit
Supplement...
3. Exams.
Daily exams will be given at the beginning of most lectures. No
make up exams will be given, but the two lowest will be dropped.
Attendance is expected. If you miss a daily exam it will count
toward one of the two dropped exams. For scheduled hourly exams,
no make up exams will be given. You must take the exams on the
dates and times as scheduled.
4. Final exam.
The final exam will be comprehensive.
5. Homework.
Daily homework will be assigned. It is due at the beginning of
the following lecture period. Penalty points will be assigned for
missing or late homework.
6.
Prerequisites.
The prerequisite for this course is completion of both semesters
of General Chemistry. A corequisite is enrolment in CHE-311.
2
7. Office Hours.
The instructor is available at any time outside of class for
questions, etc. Do not hesitate to seek help if you need it.
8. Cheating. Don't do it! At best you will receive a failing
grade and be put on academic probation, at worst you will be
expelled from the university.
Review the University Catalog
statement on Academic Integrity!
9. Course goals, objectives and requirements are covered in the
rest of this syllabus.
3
CHE-310
Meeting
1.
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44.
TENTATIVE SCHEDULE
Date
8/26
8/28
8/30
9/2
9/4
9/6
9/9
9/11
9/13
9/16
9/18
9/20
9/23
9/25
9/27
9/30
10/2
10/4
10/7
10/9
10/11
10/14
10/16
10/18
10/21
10/23
10/25
10/28
10/30
11/1
11/4
11/6
11/8
11/11
11/13
11/15
11/18
11/20
11/22
11/25
12/27
11/29
12/2
12/4
12/6
TBA
Chapt.
1
1
1
no class
2
2
2
3
3
3
***
4
4
4
5
5
5/7
6
6
6
***
8
8
9
9
9
9
10
11
11
12
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13
13
13
14
15
15
15
16
16
no class,
16
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***
Fall '02
Topic
Introduction/Basic Principles
Basic Principles
Basic Prinicples
Methane
Methane
Methane/Alkanes
Alkanes
Alkanes
Alkanes
EXAM I ***
Stereochemistry
Stereochemistry
Stereochemistry
Alkyl Halides
Alkyl Halides
Alkyl Halides
Alcohols
Alcohols/Ethers
Ethers
EXAM II ***
Alkenes, synthesis
Alkenes, synthesis
Alkenes, reactions
Alkenes, reactions
Alkenes, reactions
Alkenes, reactions
Stereochemistry
Dienes
Dienes
Alkynes
EXAM III ***
Alicyclics
Alicyclics
Epoxides
Aromatic Hydrocarbons/Benzene
Electrophilic Aromatic Substitution
Electrophilic Aromatic Substitution
Electrophilic Aromatic Substitution
Arenes
Arenes
Thanksgiving holiday
Arenes
EXAM IV ***
TBA
FINAL EXAM ***
1
CHEM-310
Information re Exam I
In studying for your first exam in this course, you should first
go over all of the homework assignments and make sure that you
understand them.
In fact, you should be able to do any of the
assigned homework problems on the exam.
This is more difficult
than doing the homework when you have access to your notes, etc.
One way to prepare would be to redo all of your homework as if it
were an exam.
Then, pay particular attention to those problems
that you cannot do or do not understand. If you have questions
about any of the assigned material you should seek help
immediately.
- be able to define important terms.
- from atomic numbers be able to give the numbers of protons and
electrons in a neutral atom.
- be able to give spectral notations for neutral atoms.
- be able to identify ionic and covalent bonding.
- be able to draw Lewis dot structures for simple molecules.
- state the types of hybrid orbitals used in simple molecules and
give their angles.
- know the relative strengths of some simple acids and bases.
- for acid base reactions, be able to predict if a reaction takes
place, or if the reaction is given, label the stronger and weaker
acids and bases.
- be able to predict which compounds are polar.
- predict the important products of the reactions of methane.
- be able to name alkanes.
- know the mechanism for free radical halogenation of alkanes.
You may be asked to propose a similar mechanism for a reaction you
have not done!
- be able to calculate enthalpy changes, given bond dissociation
energies.
- be able to graph P.E. changes and label all parts of the graph.
2
- be able to estimate Energies of activation and predict which
step in a mechanism is rate determining. Know the importance of
Eact to the rates of chemical reactions.
- be able to draw hypothetical structures for transition states.
- understand the Hammond Postulate
- draw Newman projections for conformations in alkanes.
- be able to write equations to show how you would synthesize
alkanes in the laboratory, given the starting materials.
- be able to predict the organic products of the reactions of
alkanes.
3
CHE 310
Information about Exam II
Your second exam will cover the chapters on stereochemistry,
alkyl halides, alcohols and ethers. To study for this exam you
should go over your homework assignments. It will also help to
write your own version of the exam and trade with another
student. Try to boil the subject down to the basic principles.
This exam will have a section on stereochemistry. You must be
able to correctly specify R/S for stereoisomers (you may bring a
model to the exam). You must know the definitions of the terms
from this chapter, and understand what is important for each of
the types of reactions of chiral molecules that you might
encounter.
For alkyl halides, alcohols and ethers, be able to name compounds
correctly (nomenclature). Where necessay, be able to specify
congiguration in the name.
Know the two new mechanisms that we have learned in these
chapters: SN2, SN1. Know which mechanisms go with which
reactions under which conditions. Be able to write out all steps
in the mechanisms for given reactions and label the RDS.
Be able to predict the organic products of the reactions of alkyl
halides, alcohols and ethers. This is where you will be tested
on the particulars of a reaction such as rearrangements,
stereochemistry, and orientation.
Know how to synthesize any alkyl halide or ether from a given
starting material. Some of the methods used in syntheses may
also be covered in the part of the exam on reactions or
mechanisms.
Pay particular attention to those homework problems that are of
the above types. If you have any questions about the material,
please do not hesistate to come see me.
J. Lyle
4
CHE 310
Homework # 1
1. Read Chapter 1 of your text.
2. Define the following terms: Organic chemistry, Pauli
exclusion principle, Atomic orbital.
3. For each of the following, state how many protons are there
in the nucleus? how many eletrons are there in shells about the
nucleus? Give the spectral notation (1s22s2...): Na, Cl, Ne, Cl, Na+, O, O2-, Br, Ar, Br-, I, C.
5.
On page 5 of your text: 1.1 (a,b,c,d), 1.2 (a,b,c,d)
CHE 310
1.
Homework # 2
Define the following terms: Ionic bond, Covalent bond.
2. What kind of hybridization is used by the central atom in
each of the following compounds and what are the approximate bond
angles?
CH4
BF3
BeCl2
NH4+
CH3+
(CH3)3B
BF43. Draw Lewis dot structures to show the bonding in the
following covalent compounds:
NH3
H2O
H3O+
NH4+
CO2
5
CHE-310
1.
Homework # 3
In your text do problems: 1.6 on page 26, 1.9 on page 35,
1.11 (a) page 36, 5 (a thru f).
2. In the following reactions, label the acids and bases
involved, and label each as stronger or weaker.
H3O+
+
HCO3-
NaCN
+
H2O
NaCl
+
HI
CH3MgBr
+
---->
H2CO3
<------->
H2O
HCN
HCl
--->
+
+
H2O
NaOH
+
CH4
NaI
+
Mg(OH)Br
3. Define the following terms:Lewis acid, Lewis base,LowryBronsted acid,Lowry-Bronsted base,isomers.
CHE 310
1.
Homework # 4
Read Chapter 2
2. Predict the important products of the following reactions; if
no reaction takes place, write N.R.:
A)
CH4
B)
6CH4
C)
CH4
+
H2O, 850o,Ni---->
D)
CH4
+
Br2,hv ----->
E)
CH4
+
Cl2
F)
CH4
+
(xs)Cl2,heat ---->
3.
+
(xs)O2,flame
+
---->
O2, 1500o ---->
---->
Name the following compunds, giving two names for each:
CH3I
CH2Br2
CHCl3
CBr4
4. Write all steps in the free radical substitution mechanism
for the chlorination of methane. Label the initiating,
propagating, and terminating steps. Label the rate determining
step (RDS).
6
CHE 310
Homework # 5
1. Calculate the enthalpy change (delta H) for the following
reaction.
heat
CH4 + Br2 ------> HBr + CH3Br
2. Outline all steps in the mechanism for the above reaction,
and calculate the delta H for each step in the mechanism.
3. Draw a graph of the potential energy changes in the second
step of the above mechanism. (the graph can be free hand, but
should have all parts labeled.)
4. Draw a graph of the P.E. changes in the third step of the
mechanism.
5. An alternate mechanism for chlorination of methane was
proposed by a student and contained the following two propagating
steps:
(2)
(3)
Cl. + CH4 ----> CH3Cl + H.
H. + Cl2 ----> HCl + Cl.
Calculate the delta H for each of the above steps.
Why does the chlorination of methane proceed by the mechanism in
the text and not by this alternative route?
7
CHE 310
Homework # 6
The compound HOCl (hypochlorous acid) reacts with the compound
C6H5CH3 (toluene) under the influence of ultraviolet light as
shown in the following equation:
hv
C6H5CH3 + HOCl ------> C6H5CH2Cl + HOH
The bond dissociation energies pertinent to the above system are:
C6H5CH2-H
1.
85;
HO-Cl
60;
C6H5CH2-Cl
68;
H-OH
119 Kcal/mole
Calculate the enthalpy change for the reaction.
2. Write a stepwise mechanism for the above reaction and label
the initiating and propagating steps. (Take the bond
dissociation energy values into account when considering the most
likely mechanistic steps.) Write two possible terminating steps.
3. Calculate the enthalpy changes for the steps in your
mechanism, where possible.
4. Draw a graph of the potential energy changes for the third
step in your mechanism. Label all parts of the graph.
5. Estimate the Energies of Activation for each of the
propagating steps in the mechanism.
6. Which of the steps is the RDS (rate determining step)?
do you know?
How
7. Draw a hypothetical structure for the transition state for
step 2 of the mechanism.
8
CHE-310
1.
Homework # 7
Read Chapter 3.
2. Draw the Newman Projections for the following conformations
about the C2-C3 bond in n-butane: anti, gauche, CH3-H eclipsed,
and CH3-CH3 eclipsed. Which of these are stable conformations?
3.
Name the following structures:
CH
3
CH3CH2CH2CH2
CH3CH2CH2CH2CH3
CH3 CH3
CH3CHCH2CHCH2CH3
CH3
CH3CH2CCH3
CH3
CH3
CH2
CH3
CH CHCH CH CHCH
3
2 2
3
CH3
CH2
CH3
CH3
CH CH CHCH CHCHCH CH
3 2
2
2 2
CH2
CH2
CH3
4.
Draw all nine isomeric heptanes (C7H16) and name each one.
CHE-310
Homework # 8
page 99
3.9, 3.10,3.11
page 121
8, 9 (a,b,c)
9
CHE-310
Homework # 9
1. In your text: p. 103:3.12;3.14 (predict the products and
circle the major product. Do not predict the proportions.)
p. 121;10 (and circle the major product.)
2. Outline all steps in the mechanism for the bromination of
ethane. Label the RDS.
CHE 310
1.
Homework # 10
Read Chapter 4.
2. Define the following terms: stereochemistry, optical
acitivity, dextrorotatory, levorotatory, specific rotation,
chirality, chiral center, enantiomers, racemic
modification,configurations.
3.
4.3; 4.4; 4.5 (a-d); 4.8; 4.10 (a).
CHE-310
Homework # 11(a)
1. Define the following: diasteromers, meso compound,
resolution
2.
In your text: 4.12 (a,b,h); 4.13.
CHE-310
1.
Homework # 11(b)
In your text: 4.24.
2. For each of the following reaction types, write a sentence or
two to indicate the sterochemical importance of that type of
reaction, or the basic principle to keep in mind about that type
of reaction.
a) a reaction of achiral compounds in which a
chiral center is generated.
b) a reaction of a chiral compound in which no bonds to the
chiral center are broken.
c) a reaction as in c) where a new chiral center is formed.
d) a reaction of a chiral molecule with an optically active
reagent.
e) a reaction of a chiral molecule in which a bond to the
chiral center is broken.
10
CHE-310
Homework # 12
1.
Read Chapter 5.
2.
In your text:
3.
Outline all steps in a possible laboratory synthesis of:
p. 211: 2; 3; 4;
a) n-propyl bromide from n-propyl alcohol,
TWO WAYS.
b) isopropyl iodide from isopropyl alcohol, THREE WAYS.
CHE 310
Homework # 13
In your text:
5.2; p. 212: 5; 6(a).
Predict the product(s) of the following reaction.
the stereochemistry of the product(s).
CH3
¦
H ---+--- Br
¦
CH2CH3
+
NaOH
You must show
SN2
----->
Using "curved arrow formalism", outline all steps in the
mechanism for the following reaction and label the RDS.
CH3Br
+
NaOH
----->
CH3OH
+
NaBr
Draw a hypothetical structure for the transition state of the RDS
in the above mechanism. What is the name of this mechanism?
11
CHE 310
Homework # 14
Predict the product(s) of the following reaction.
stereochemistry of the product(s):
CH3
¦
H ---+--- Br
¦
CH2CH3
+
NaOH
Show the
SN1
----->
Using "curved arrow formalism", outline all steps in the
mechanism for the following reaction and label the RDS.
CH3
CH3C-Br
CH3
+ dilute NaOH
----->
CH3
CH3C-OH
CH3
+
NaBr + alkene
Draw a hypothetical structure for the transition state of the RDS
in the above mechanism. What is the name of this mechanism?
In your text:
p. 212
CHE 310
8 (a-h); p. 271
Homework # 15
page 245:1;6;
Complete the following reactions:
CH3
CH3CHCHCH3
+ HBr ----->
OH
CH3CH2CH2CH2OH + HI ----->
p. 247
read "About Syntheses"
17 (a,b,d,e,h).
4 (i,j);
12
CHE-310
Homework # 16
Outline all steps in the mechanism(s) for the reactions: Don;t
forget to use "curved arrows" to show the movement of electron
pairs. Label the RDS. Name each mechanism!
CH3CH2-OH
+
tert-butyl alcohol
HCl
+
H+
----->
HBr
CH3CH2-Cl
H+
----->
+
H2O
tert-butyl bromide
+
H2O
Give the structures of the organic products expected for the
following reactions:
1.
n-butyl alcohol with
a) sodium bromide, sulfuric acid
b) ethyl magnesium bromide (CH3CH2MgBr)
c) sodium bicarbonate (NaHCO3)
d)
f)
K2Cr2O7
C H NHCrO Cl
5 5
3
CH3SO2Cl,OH-
g)
acetic acid (CH3COOH),H+
e)
2.
sec-butyl alcohol with
a) P,I2
b)
c)
d)
e)
NaOH
Na
NaOCl (bleach)
CrO3
C6H5COOH,H+
tert-butyl alcohol with
a) HI
b) NaNH2
f)
3.
c)
d)
e)
K
product of c) + ethyl iodide
KMnO4
f)
Br2
13
CHE-310
Homework # 17
page 245: 2;3;7. Outline Williamson Syntheses for each of
the ethers in problem 3.
CHE-310
Homework # 18
In your text: 8.1 (a) and name each compound (use E/Z for
geometric isomers); 8.2; 8.5 and circle the major product if more
than one is formed; 8.6 ( note: you want the alkyl halide that
will give only one organic product from the dehydrohalogenation,
not a mixture!);
p. 316:6 (a,b,c,e); 7 (a,b,c,e).
Outline all steps in the mechanism for the following reaction.
Label the RDS.
CH3CH2Br + KOH(alc) -----> CH2=CH2 + H2O + KBr
CHE 310
Homework # 19
1. Predict the products of the following reactions. If more
than one organic product is produced, circle the major product.
a)
n-butyl bromide
+
KOH(alc) ---->
b)
n-butyl alcohol
+
H+
c)
neopentyl alcohol
d)
2,3-dibromopentane
+
+
---->
H+
Zn
---->
---->
2. Outline all steps in the mechanism for the following
reaction. Label the RDS.
isopropyl alcohol + H+ ----> propylene
3. Why is dehydrohalogenation of an alkyl halide often preferred
over dehydration of an alcohol in the synthesis of many alkenes?
4.
p. 316:
13.
14
CHE-310
Homework # 20
In your text: Page 363: 1 (a-j);
20 (a,b); 21 (a).
3 (a thru e);
Page 366:
Outline all steps in the mechanism for the following reaction:
Label the RDS. Name the mechanism.
CH2=CH2
CHE-310
In your text:
21 (b, c, d).
CHE-310
In your text:
+
HBr
----->
CH3CH2Br
Homework # 21
page 363: 1 (k thru n);
page 366: 20 (c, d, e);
Homework # 22
Page 363:1 (s,t);Page 363: 4.
Outline all steps in the mechanism of the following reaction:
Label the RDS. Name of the mechanism?
H+
CH2=CH2 + H2O -----> CH3CH2-OH
Outline all steps in the mechanism for the following reaction:
Label the RDS. Name of the mechanism?
perox.
CH2=CH2 + HBr ----->
CH3CH2Br
CHE-310
In your text:
(f);21 (e,f).
Homework # 23
page 363: 1 (o thru r);16;17 (a);page 366:20
15
CHE-310
Homework # 24
Define the following terms:stereospecific reaction,
stereoselective reaction.
In your text:
10.1;10.4.
CHE 310
1.
Homework # 25
Name the following compounds:
CH2=CH-CH=CH-CH=CH-CH3
CH3
CH2=CH-C=CH2
2.
CH3-CH=CH-CH2-CH=CH2
CH3-CH2
\
H
/
C = C
CH3
/
\
/
H
C = C
/
\
H
H
predict the product(s) of the following reactions:
CH3-CH=CH2
+
Br2
CH2=CH-CH3
+
Br2
----->
heat
----->
16
Homework # 26
1.. Give the structures of the organic products expected from
the reaction (if any) of 1,3-butadiene with:
a) H2, Ni
b) 2 moles H2, Ni
c) Br2
d) 2 moles Br2
e) HCl
f) HBr, peroxides
g) KMnO4
h) Br2, H2O
2. Give the structures of the organic products expected from the
reaction (if any) of 1,4-pentadiene with each of the reagents
shown above in problem 1.
3.
In your text:
page 422
CHE 310
In your text:
Homework # 27
p. 441: 1;2;4.
CHE 310
In your text:
5 (b,f).
Homework # 28
p. 488-489:1 (a,f,h);2 (a thru h); 3 (b,h,j,k).
CHE 310
Homework # 29
In your text: 13.1;p. 488-489:1 (b,c,d,e);2 (i thru cc);3 (a,c
thru f, i, j, k).
CHE 310
13.27; 13.25; p. 491: 16.
Homework # 29-2
17
CHE 310
Homework # 30
In your text: page 515-516:
theoretical; 9.
CHE 310
In your text:
CHE 310
In your text:
p. 548:
4 (a thru f)
note the word
Homework # 31
p. 515:
2 (d,e);
Homework # 32
p. 546: 2 (all);
15 (a - g);
p. 546:
1 (all).
(two days?)
3 (all);
5.
Outline all steps in the mechanisms of the following reactions.
Label the RDS.
a) nitration
b) sulfonation
c) halogenation
d) Friedel-Crafts alkylation
CHE 310
Homework # 33
In your text:
p. 581: 1 (all);
CHE 310
In your text:
p. 581:
Homework # 34
p. 581: 3 (all);p. 584: 18 (a,b,d,e);
4 (all).
CHE 310
2 (a-h);
16.2
Homework # 35
In your text:
p. 581:
problem 4 using phenylacetylene instead of
trans-phenylpropene:(a,b,c,e,f,k,m,H2SO4 + Hg++ + H2O); 5 (all);
18 (c,g).
18
CHE 311
Instructor:
Office:
Phone:
Office Hours:
Sylabus
Dr. J. L. Lyle
NSM D-323
(310)243-3388;243-3376
Will be announced in class; open door policy
Required Texts:
Introduction to Organic Laboratory Techniques Pavia, Kriz,
Lampman & Engel.
CRC Handbook of Chemistry and Physics (highly recommended)
Lab notebook
Safety goggles
1. Grading:
Traditional letter grades will be assigned on the
same basis as in CHE-310.
Lab reports
50%
Notebook
10%
Final Exam
25%
Evaluation
15%
2. Lab reports. A typed lab report will be required for each
experiment. The report is due one week after the scheduled
completion of the lab. These reports are due at the scheduled
start time for the lab. Late reports will be penalized one
letter grade for the first 24 hours. Lab reports that are
submitted more than 24 hours late will not be accepted!
Please note that lab reports are not written in the lab notebook,
but are separate requirements. You will be given explicit
instructions about what each lab report is to contain. Lab
reports are to be your own work and not plagiarised from some
other student or lab report. Academic dishonesty will not be
tolerated!
3. Notebook. A written record of what you are doing in the lab
will be kept in your notebook. You are expected to have your
notebook with you in the lab. Failure to do so can affect your
grade. The notebook entries will be written in ink. The carbon
copies that you make will be submitted with your lab reports.
4. Final Exam. A written final exam will be given at the end of
the semester. Date and location will be announced later.
5. Evaluation. Part of your grade will be an evaluation of your
lab technique, preparedness, punctuality, etc. by the instructor.
19
6. Safety.
in the lab.
lab.
You must wear approved eye protection at all times
Failure to do so will result in expulsion from the
7. Prerequisite. You must have completed both semesters of
general chemistry. Corequisite is enrolment in CHE-310.
8. Attendance. You are expected to attend all laboratory
sessions. Make ups will only be allowed if arrangements are made
prior to the missed lab and for good reason.
9. Course goals, objectives, and requirements are covered
elsewhere in this syllabus.
20
CHE 311
Organic Chemistry Laboratory I
Week:
1.
Check in/ Orientation to lab
2.
Simple distillation
P. 706-713
3.
Fractional distillation
p. 733-744
4.
Extraction
p. 685-693, p.696-699
5.
Steam distillation
p.753-761
6.
Recrystallization
p. 648-663
7.
8.
9.
10.
11.
"
& melting point
Chromatography
p. 666-674
p. 792-806, p.761-770
"
p. 808-823
Alkyl Halide Syntheses
p. 204-211
"
12.
Dehydration of 4-methylcylcohexanol
p. 248-252
13.
Nitration of a halobenzene
14.
"
15.
Check out
16.
TBA
Final Exam
see sylabus
21
CHEM 311 ORGANIC CHEMISTRY
NOTEBOOK
Your notebook is to be with you at all times in the laboratory.
This is where you record what you have done and all of the data
and obsevations that you take. Note that the lab notebook is not
the lab report. Lab reports are written separately and the
carbons from your notebook are attached to the end of the report.
Please use the following format for your lab notebook entries:
Title of experiment
(be specific)
Name
Date
Unk # (if any)
A step by step description of what you did (it must contain
sufficient detail so that the experiment could be repeated by
anyone reading your notes). One technique is to write in the
steps you propose to do before you get to the lab and then add
additional comments and observations as you actually do the lab.
All significant observations and measurements must be recorded
directly into the notebook. Do not record data on other sheets
of paper for later transcription into the notebook!
The original (white) sheets remain attached in the notebook, the
carbon copies (blue or yellow) will be attached to your lab
report.
22
EXPERIMENT: Simple Distillation and Determination of the Boiling
Range of an unknow organic liquid
Read p. 706-713 in your lab text!
The principal purposes of this exercise are to familiarize
you with the mechanics of the distillation technique and to
permit you to observe the behavior of a single substance when it
is distilled. You may regard this to be the situation in which a
new compound whose actual boiling point is not known has just
been made. You are in effect carrying out the last step of the
preparative procedure - distilling the compound to purify it and
at the same time measuring its boiling range.
You have an “unknown” organic liquid at your desk; record its
number in your notebook.
Procedure
All glassware must be dry!
(water is a compound!)
Do not wash the glassware that is to be used for the
distillation, unless it is obviously dirty. If you do wash them,
all glass parts must be thoroughly dried before the apparatus is
assembled.
Three ring stands are necessary to construct the
distillation assembly described below. Be sure that the ring
stand bases face forward (toward you) and are parallel with one
another. Three clamps and one iron ring are needed. If they are
available, 3-prong clamps should be used to support the condenser
and the receiver; a burette clamp is best for the still pot.
1.
Select a distilling flask of appropriate size (the still pot
should be about half-full initially). The receiver for this
distillation is a graduated cylinder large enough to contain
the volume of sample you are given. Ordinarily, an
Erlenmeyer or round-bottom flask, or even the bottle in
which the product is to be packaged, is used as the
receiver. You use a graduated cylinder here because you are
to obtain a record of distillate volume vs. vapor
temperature.
2.
Set up the apparatus as shown on page 711 of your lab text
and in the sample assembly in the laboratory. Pay
particular attention to the following points:
23
a.
b.
c.
d.
e.
f.
g.
h.
i.
3.
Build the apparatus from the "bottom up." Begin by
clamping the receiver (a graduated cylinder) to a ring
stand.
If you are using standard-taper ground-glass-joint
glassware, be sure to put a thin film of lubricant on
the joint surfaces.
Arrange the assembly so that the receiver is as close
to the end of the condenser as possible. To ensure
that the flow of distillate from the condenser to the
receiver is true, a bent adapter may be attached to the
end of the condenser. The lower end of the adapter
should protrude into the cylinder, but should not be
"jammed" into the opening. The junction is not meant
to be airtight.
Should you find that the receiver is too far from the
end of the condenser (with or without an adapter),
raise the receiver by clamping it to the ring stand.
Do not use books, sponges, inverted beakers, etc., to
support any part of the apparatus.
Make sure that the space between the flask bottom and
the ring stand base below it is sufficient to allow
easy placement and removal of the heating device.
The thermometer must be perfectly vertical. If it is
not, make whatever adjustments are necessary in the
angle of the condenser. If you experience any
difficulty ask your instructor for help.
The top of the thermometer bulb must be level with the
bottom of the sidearm opening of the still head.
Make certain that there are no kinks or restrictions in
the rubber tubing through which the cooling water flows
to and from the condenser. The tubing must be long
enough to reach from the water source to the inlet tube
of the condenser, and from the condenser to the drain.
If only short pieces are available, they may be joined
with short lengths of fire polished glass tubing or
special plastic connecting tubes.
Turn on the cooling water cautiously! If the valve if
opened too quickly, the pressure may force the rubber
tubing from the condenser connection, and you and your
neighbors may get an early shower.
If a heating mantle is to be used, observe the following
precautions:
a.
The mantle must be of the proper size to fit exactly
around the flask (unless the heating unit is of the
type that may be used for several flask sizes). The
size is usually specified on a tag attached to the
mantle or the cord.
24
b.
c.
The heat input is controlled by means of a variable
transformer, to which the mantle cord should be
connected. Do not plug the cord directly into the line
outlet unless the mantle has a built-in variable
control.
The mantle should be supported by an iron ring or other
suitable device (not books!) so that it is at least
several inches above the bench top and can be lowered
away from the flask when necessary. Do not rest the
mantle directly on the bench surface.
5.
Pour the liquid sample into the still pot. Use a funnel
with a stem long enough to reach past the sidearm opening.
6.
Add three or four boiling chips to the still pot.
7.
Make certain that water is flowing in the proper direction
through the condenser jacket.
8.
Heat the liquid until boiling commences. Adjust the flame
or transformer setting so that gentle boiling is maintained.
Apply aluminum foil insulation unless you are directed not
to do so by your instructor.
9.
Distill the liquid and follow the procedure as below.
Note the temperature when the first drop of distillate is
collected. Record the temperature when the first volume
measurement in the graduated cylinder is feasible, and at
intervals of 1 or 2 mL of distillate collected thereafter.
Do not distill the liquid to dryness. Stop the distillation
when a few drops remain in the still pot.
10.
Stop the distillation by turning off the flame or the
transformer. If a heating mantle was used, lower it away
from the still pot. Allow the flask to cool for a few
minutes before disassembling the apparatus.
11.
Pour the distillate and any residue in the still pot back
into the bottle in which the sample was received. Return
the bottle to the place designated by your instructor.
25
Interpretation of Results and the Report
In addition to learning the technique of performing a
distillation, you have had the opportunity to observe at first
hand the behavior of a reasonably pure compound in the
distillation process. You also measured quantities
(temperatures) whose magnitudes you did not know before-hand.
Your report (see next page) should include the following:
1.
A brief introductory discussion, in your own words, of
the physical principles involved in the distillation of a liquid.
2.
The Experimental section, in which you describe in
your own words the procedure you have carried out. A tabulation
of the volume and temperature measurements must be presented.
The atmospheric pressure at the time of the distillation, if
known, should be noted as well.
3.
A brief Discussion of Results, excluding details of
experimental procedures. This part provides the interpretation
of the accumulated data and other pertinent observations. A
graph of vapor temperature vs. distillate volume would be most
helpful in presenting the conclusions to be drawn from the
experimental results. An indication of the relative amount of
forerun, if any, and the corresponding temperature range over
which it was collected should be cited.
The boiling range of the distillate collected in a
single container must be reported. As an example, consider the
following distillation in which no forerun was collected
separately. The temperature at which the first drop was
collected was 110oC. The distillation was stopped when the
still-head temperature registered 122oC.
The boiling range of
the distillate in that case was therefore 110-122oC. (Note that
the boiling range has a beginning value and an end value. Thus,
the range in the example is not 122o, but is 110-122oC.) If 5 mL
of forerun were collected first, and the main body of distillate
o
o
(32mL) then collected from 120-122 C, the 120-122 C range is the
boiling range of the major portion of the liquid.
Some comment on the appearance of the liquid before and
after distillation is in order, as is any other significant
observation.
Note: It is not considered good form to use the first person
pronouns I or we in chemistry reports. Instead of “I added
30 mL” , write instead “Thirty mL was added.”
(Use passive
voice)
26
CHE 311
Lab Report for Simple Distillation
Your lab report for the first experiment should follow the format
and consist of the following:
Title(be specific)
name
date
section number
Unknown #
Introduction
(give a brief statement about what a simple
distillation is and is used for and how it works. Then
state concisely what is to be done in this experiment. Do
not draw the apparatus! Do not state a "purpose".)
Data
(a table of the data collected, suitably labeled)
(a graph of the data. Use mm graph paper and make the
graph professional. Do not use pages from the lab
notebook!)
Results
(a paragraph describing any observations or conclusions.)
(See previous page)
Exercises
1. In a short paragraph, describe how simple distillation
separates two compounds with different boiling points.
2. If the thermometer is placed below the outlet to the
condenser, will the temperature measured be correct? If not,
will it be higher or lower than the actual vapor temperature?
3.
What are boiling stones and why are they added?
4. Describe the observations that one would make during the
simple distillation of a "pure" substance.
5. What happens to the still head temperature during the
simple distillation of an "impure" substance.
6. At 30oC, the vapor pressures (in torr) for methanol and
ethanol are 350 and 180, respectively. Given a mixture at 30
degrees that contains 0.2 mole of methanol and 0.1 mole of
27
ethanol, compute the partial pressures of each liquid and the
total pressure.
7. In a simple distillation, you measure a boiling range
that is 110-112 degrees; How pure do you think the liquid sample
is? Explain
8. You have just completed a simple distillation and have
made observations of the temperature as the distillate is
collected. How would you know whether your distillation was
successful and that the distillate is reasonably pure?
Answer the questions on Page 716 of your lab text.
Attach the carbon copies from your notebook.
28
EXPERIMENT:
Fractional Distillation of a Two-Component Mixture
Read 733-745 in your lab text!
This exercise is intended to demonstrate the behavior of a
pair of miscible liquids in a simple distillation, and to
familiarize you with the technique of fractional distillation
with a column. You will first carry out and observe the
characteristics of a simple distillation of a mixture. Then the
same mixture will be distilled through a fractionating column.
Please note that the fractional distillation may not be
completely effective - the column may not be efficient enough
because of the kind and amount of packing used, or because of
insufficient length, and heat losses due to inadequate insulation
may contribute to less than perfect results. Since the
distillation is to be conducted using continuous takeoff (nearzero reflux ratio), the best possible conditions for
fractionation cannot be realized.
Bear in mind that the purposes of the experiment are to
demonstrate the distillation behavior of a mixture of miscible
liquids and to acquaint you with the basic technique of
fractional distillation. Your goal is not to determine the
boiling point of either component, nor is it to achieve a perfect
separation.
Procedure
A.
Simple Distillation of the Mixture
All glassware must be dry!
1.
2.
B.
Set up a simple distillation apparatus. Use a 250-mL flask
as the still pot. A 50-mL graduated cylinder serves as the
receiver.
Be sure to add boiling chips to the flask.
Distill the unknown mixture as in the previous experiment
1.
Note the still-head temperature when the first drops of
distillate appear, and record the vapor temperature at
intervals of 1 or 2 mL of distillate thereafter.
2.
Continue the distillation and collection until the
still pot is almost dry.
Fractional Distillation of the Mixture
1. Set up a fractional distillation apparatus by inserting
a fractionating column packed with steel wool between the still
pot and the still head adapter.
29
2. Add a couple of fresh boiling chips to the still pot and
using the liquid funnel, add the mixture that you distilled in
the simple distillation.
3. Distill the unknown mixture as in the previous
experiment, noting the still-head temperature at the first drop
and every 1 or 2 mL of distillate thereafter. Continue the
distillation until the still pot is almost dry.
4.
Allow the still pot to cool. Pour the distillate and
the distillation residue back into the sample bottle.
Return the bottle to the designated place in the
laboratory.
5.
Disassemble the apparatus. If your fractionating
column is packed with stainless steel sponge, do not
wash it with water.
Interpretation of Results and the Report
Follow the same format that was used in writing the report
for the exercise on simple distillation of a single liquid.
Of particular importance in the interpretation of your
observations is a comparison of the simple distillation of the
mixture with the distillation of the same mixture through a
fractionating column. A tabulation of temperature-volume data
for each distillation serves as the basis for the construction of
two graphs, one for the simple and one for the fractional
distillation.
Some comment on the efficacy of the distillation using the
column should be offered. For example, the data you obtained may
have indicated that the fractions collected were mixtures,
although of different composition than the original. Thus an
ideal separation may not have been achieved because of
deficiencies in the apparatus (or your technique?). Some
recommendations about improvement of the fractionation assembly
and conduct of the distillation are then in order. The primary
purpose of the experiment was not a determination of the boiling
points of the components, so do not dwell on the aspect of it.
Remember, too, that it is not necessary to go into great
detail in either the preliminary discussion or the Experimental
section about the simple distillation procedure used in this
experiment. It is sufficient to state that the mixture was
subjected to a simple distillation and to give the results of
that operation. A full account of the fractional distillation,
including details of the apparatus used, should be given since it
is being reported by you for the first time.
30
CHE 311
1.
As before:
Report for fractional distillation
title (specific)
name
date
CHE 311-0x
unknown #
2. In your own words, explain how fractional distillation works
to separate volatile liquids.
3. In one or two sentences, summarize what you did in this
experiment.
4.
Make a table of the data you collected.
5. Attach a graph (neat and professional on mm graph paper) of
the still head temp. vs. volume collected for the simple
distillation. On the same graph, plot the data for the
fractional distillation in a different color.
6. Describe the results you obtained from the simple and
fractional distillation. See if you can put into words the data
that you collected and the resultant graph.
7. What conclusions can you make from the results of your
experiment? Compare the two methods for efficacy. If you have
an opinion, back it up with data. See previous page.
8.
Answer the following questions:
a.
What is Raoult’s Law?
b.
What is Dalton’s Lay?
c. Describe how Raoult’s and Dalton’s Laws relate to fractional
distillation as a separation technique.
d. What’s the difference between a packed column and an unpacked
column a fractional distillation?
e.
What is a theoretical plate?
f. On page 735 of your lab text is a temperature composition
diagram for mixtures of two compounds, A & B.
(1) From the graph, what are the boiling points of pure A & pure
B?
31
(2) For a mixture that contains 60 mole% A and 40 mole% B, what
is the boiling point? what is the composition of the first
distillate and if this distillate were to be condensed, what at
temperature would it boil? what is the composition of the vapor
at this temperature?
(3) For a boiling mixture at 70oC, what is the composition of the
vapor and the composition of the liquid?
g. At what point do you change receivers during a fractional
distillation if you are trying to separate the components?
h. What observations during a simple distillation would cause
you to redo the distillation using a fractionating column?
Answer questions 1, 4 on Page 752 of your lab text.
9.
Attach notebook carbon copies.
32
EXTRACTION
Read p. 685-693, 696-699 in your lab text.
Extraction is a separation technique based on differences in
solubilaiies of substances in two immiscible solvents (usually
water and a water insoluble organic solvent).
solubility in solvent 1
Kc = partition coefficient = ------------------------solubility in solvent 2
example:
Given compound A, Kc (ether:water) = 4.0, how much of A
can be extracted from a solution of 10.0 g of A in 100 mL of
water with a single portion of 100 mL of ether?
X / 100 mL ether
Kc = 4.0 = -------------------(10.0 - X) / 100 mL water
X = 8.0 grams of A extracted into the ether
-same as above, but extract two times with 50 mL of ether each
time.
X / 50 mL ether
first extraction:
Kc = 4.0 = ------------------(10.0 - X) / 100 mL water
X = 6.67 grams of A extracted
second extraction:
Kc = 4.0 =
Y / 50 mL ether
------------------(3.33 - Y) / 100 mL water
Y = 2.22 grams of A extracted
total extracted =
X + Y = 6.67 + 2.22 = 8.89 grams
33
==> multiple extractions with smaller amounts of solvent are
more efficient than a single extraction with the same total
amount of solvent.
DRYING: an organic liquid that has been in contact with water is
"wet" (contains some water). To "dry" it, use an inorganic
drying agent. See Table 2.1 in your lab text.
"WASHING":
extraction to remove an unwanted compound.
Today's experiment:
HCl
CH3CH2CO2-Na+
------>
sodium propionate
(solid)
CH3CH2CO2H
propionic acid
(liquid)
Your unknown contains an unknown % of sodium propionate. It is
not necessary to weigh the unknown before you begin the
experiment, assume that it weighs 30.0 grams. You will convert
the solid sodium propionate into propionic acid by reacting it
with hydrochloric acid. Propionic acid is both water and ether
o
soluble, has a bp of 141 C, and forms an azeotrope with water.
To remove the propionic acid from the aqueous solution, you will
extract with three 40 mL portions of diethyl ether. Do not throw
anything away until you are absolutely certain you have kept the
right layers. After combining the three ether extracts, dry them
over anhydrous magnesium sulfate. Fractionally distill off the
diethyl ether (<100oC). Then set up for simple distillation and
simple distill the propionic acid, collecting as your final
product all material boiling above 135oC. Package your product
and label the bottle according to instructions below.
turn it in with your report next week.
You will
Note: Propionic acid is a “common” name. The IUPAC name for
this compound is propanoic acid. It will be found in the CRC
handbook under its IUPAC name.
“Salting Out” The addition of NaCl to an aqueous solution
containing an organic compound will decrease the solubility of
that compound in the aqueous solution. This is called “salting
out.” Apparently, the salt increases the ionic strength of the
solution, making it more polar and the weakly polar or non-polar
organic compound is less soluble.
34
EXPERIMENT: Formation of a Water-Soluble Liquid Organic Acid
and Its Extraction from an Aqueous Solution
In this experiment, a simple reaction followed by an
extraction to separate the desired product from solution will
illustrate a typical application of extraction.
Some liquid organic acids are very soluble in water. The
sodium salts of these acids are ionic solids that are also very
soluble in water. If an aqueous solution of one such salt is
acidified with a strong mineral acid (e.g., hydrochloric or
sulfuric acid) the weaker organic acid is produced, as is shown
in the following representative equation:
Na+ + CH3CH2CO2- + H3O+ + Cl- --->
sodium propionate hydrochloric
acid
CH3CH2CO2H + Na+ + Cl- + H2O
propionic
acid
(AKA propanoic acid)
The organic acid is largely unionized in the water solution.
No apparent change will be observed when the reaction is
carried out because the solutions of the starting materials are
colorless and the resulting solution containing the indicated
products is also colorless. The acid is completely soluble in
water and, thus, does not separate. Although propionic acid has
o
a boiling point of 141 C, it cannot be separated from the water
by fractional distillation because the two liquids form an
azeotrope (bp 99.9oC; 17.7% propionic acid, 82.3% water).
Therefore, it is necessary to resort to extraction with an
organic solvent in which the organic acid is quite soluble.
After drying the organic solution, the organic solvent may be
removed by fractional distillation and the residual propionic
acid purified by a simple distillation.
You will receive about 30 g of an unknown mixture of solid
salts which contains 50-90% sodium propionate, the remainder
being an inert inorganic salt.
Procedure
1.
2.
3.
4.
Place all of the unknown containing sodium propionate in a
250 mL beacker.
Add 100 mL of distilled water to the beaker and stir the
mixture with a glass rod.
Pour 60 mL of 6 M hydrochloric acid into the sodium salt
solution, while stirring with a glass rod.
Transfer the aqueous solution to a 250-mL separatory funnel.
(Be sure that the stopcock is closed and that a beaker is
placed beneath the funnel.)
35
5.
The aqueous solution is to be extracted with three 40 mL
portions of diethyl ether as follows:
a.
Add 40 mL of the solvent to the solution in the funnel.
Perform the extraction.
b.
Drain the lower aqueous layer into the beaker, and pour
the ether solution through the top of the funnel into a
250-mL Erlenmeyer flask.
c.
Repeat the extraction twice more with 40 mL of diethyl
ether each time.
DO NOT DISCARD ANY OF THE SOLUTIONS UNTIL YOU HAVE REACHED STEP 9.
6.
Add just enough anhydrous magnesium sulfate to the combined
ether extracts to just cover the bottom of the flask. Seal
the flask with a cork stopper that does not extend more than
half its length into the flask neck. (Note: If the
magnesium sulfate dissolves, you goofed! Go back through
your procedure to see where you made the error.) Swirl the
contents of the flask gently and allow the mixture to stand
for at least 30 minutes. If necessary, you may let the flask
stand until the next laboratory period.
7.
Set up a fractional distillation apparatus, using a 250-mL
round-bottom flask as the still pot. The receiver is a 250mL Erlenmeyer or round-bottom flask. Surround the receiver
with a small plastic bowl containing a mixture of ice and
water.
8.
Remove the still pot from the assembly and support it on a
cork ring. Place a narrow-stem funnel in the flask neck, and
insert a small plug of absorbent cotton at the top of the
funnel stem.
9.
Carefully decant the ether solution from the drying agent
through the funnel into the flask. Rinse the Erlenmeyer
flask containing residual drying agent with about 10 mL of
ether and add the rinsings to the still pot. (Note: None of
the drying agent should have entered the still pot. If some
did, empty the still pot into the Erlenmeyer flask, and
refilter the mixture into the round-bottom flask.)
10.
Add three or four boiling chips to the still pot and reattach
the flask to the fractionating column.
11.
Slowly distill the ether from the solution. When distillate
collection slows markedly or stops, or if the still-head
temperature reaches 100C, discontinue the distillation. Do
36
not attempt to distill the propionic acid through the
fractionating column.
12.
13.
14.
15.
16.
17.
18.
Allow the still pot to cool for several minutes. Then remove
the fractionating column and receiver from the assembly.
Pour the ether from the receiver into the special container
labeled Recovered Ether from Extraction or Waste Organic
Solvent.
Transfer the residual liquid in the still pot to a 50-mL
round-bottom flask and incorporate the smaller flask in a
simple distillation assembly.
Place two or three fresh boiling chips in the still pot and
start the simple distillation.
Collect as forerun any distillate obtained up to a still-head
temperature of 135oC. Then carefully change receivers,
placing a preweighed narrow-mouth bottle in position to
collect the propionic acid.
Continue distilling the product, measuring the boiling range
simultaneously. Do not distill the liquid to dryness, but
leave a very small amount in the still pot.
Reweigh the receiver plus contents to obtain the weight of
the distilled propionic acid.
Label the bottle in the manner shown below.
PROPIONIC ACID
wt.:
Your name
g
br
Date
oC
The Report
In addition to a discussion of the principles of simple
extraction and the function of drying agents, the Introductory
section should include a statement of the problem - what you were
to do.
In the Experimental section, be sure to specify the
quantities of materials, as well as the weight and boiling range
of the final product. The following is an example of how this
information may be presented: "Unknown No. 12 (30.4 g) was
dissolved in 100 mL of distilled water. To the salt solution was
added 30 mL of 6 M HCL, and no apparent change was observed... .
A total of 13.2 g of propionic acid, br 136 - 142oC (lit., 141oC)
was obtained."
In the Discussion of Results, offer a comment on the purity
of the distilled acid, based on your experimental observations.
You may also calculate an approximation of the composition of the
unknown mixture. The calculation is based on the balanced
37
equation, which indicates that 1 mole of propionic acid is
obtained from 1 mole of sodium propionate.
Calculation of Approximate Composition of Unknown
The balanced equation shows that one mole of sodium propionate
yields one mole of propionic acid. From the weight of the
propionic acid that you have collected, you must first calculate
how many moles of propionic acid you have. That number of moles
is the number of moles of sodium propionate that you must have
started with. Convert the number of moles of sodium proionate to
grams of sodium propionate. That number, divided by the weight of
the unkown, times 100% is the approximate percent of the unknown
that was sodium propionate. This number is, of course,
approximate as (a) not all of the propionic acid was necessarily
extracted; (b) mechanical losses of propionic acid were suffered
during the distillation; and (c) the propionic acid obtained is
not 100% pure, and the weight of the product includes the
impurity.
38
CHE 311
1.
Report for Extraction; Drying Methods
As before:
2.
name
date
CHE 311-0x
unknown #
State in a few sentences what you did in this experiment.
3.
Include a table containing the following:
Weight of unknown
30.0
g
Weight of propionic acid
obtained
g
Moles of propionic acid
moles
obtained
Moles of unknown
moles
as sodium propionate
oC
Boiling range of propionic acid
Literature value for the boiling point of
oC
propionic acid
% sodium propionate in the original sample as
calculated based on the amount of acid
recovered
%
(note the calculation is based on the balanced
equation that indicates that 1 mole of
propionic acid is produced from 1 mole of
sodium propionate.)
4.
Answer the following questions:
A. Explain the purpose of reacting the unknown with hydrochloric
acid before the extractions?
B. A student made a mistake and did a single extraction with 120
ml of ether instead of three separate extractions with 40 mL of
ether each time. How will his results be affected?
C. A student added anhydrous magnesium sulfate to his combined
extracts and the magnesium sulfate dissolved. What error did the
student make in the experiment? What should he do now?
D. During the second extraction, a student added ether to the
layer in the separatory funnel and it did not separate. What
mistake did the student make? What should he do now?
E. How pure do you think the propionic acid is that you recovered
and how do you know?
39
F. If, in an extraction, you were uncertain about which layer was
the aqueous layer and which layer was the organic layer, how could
you quickly settle the issue?
G. Given 200 mL of an aqueous solution containing 10 g of
compound A, from which it is desired to separate A, how many grams
of A could be removed in a single extraction with 200 mL of
diethyl ether? (The distribution coefficient, diethyl ether: water
is 5.0).
H. How many total grams of A could be removed if two successive
extractions with 100 mL each were used in G?
Attach carbons
40
EXPERIMENT:
Steam Distillation
Separation of a Volatile Component from a Mixture
Read p. 753-760 in your lab text!
In certain reactions, it is not feasible to remove the
desired compound (or unreacted starting material) from the mixture
by simple or fractional distillation, or by other physical
methods. Steam distillation very often successfully effects the
separation, and does so at a temperature considerably below the
boiling point of the compound being removed. Steam distillation
is also quite useful in the isolation of natural products.
An artificial mixture is to be steam distilled to recover one
of the components. To add an element of mystery, the sample you
receive is an "unknown" in that the quantity of the recovered
compound is to be determined and reported.
The mixture to be separated is typical of that obtained in
one of the methods of preparation of compounds called haloarenes.
One byproduct of the reactions is a group of compounds called
phenols. (Some other highly colored substances are present as
nonvolatile contaminants.) Separation of the product haloarene
from the phenol contaminant by fractional distillation is somewhat
difficult because of the high boiling points of these compounds.
Steam distillation is a more convenient way of isolating the
desired product, but a pretreatment of the reaction mixture is
necessary because the phenol is somewhat volatile and would also
codistill with steam. Fortunately, the phenol is a weak acid and
the haloarene is not. Treatment of the mixture with a solution of
sodium hydroxide converts the phenol into a water-soluble,
nonvolatile ionic salt, as is shown in the following illustrative
equation.
C6H5OH + Na+ + OH- ---> C6H5O- + Na+ + HOH
phenol
base
sodium phenoxide
(acid)
(salt)
The steam distillation is to be carried out using internal
steam generation. The experimental procedure involves both the
separation of haloarene and an attempted verification of the
principles of steam distillation. The latter objective is
effected by keeping a record of the vapor temperature during the
codistillation process.
The mixture you will receive is
Phenol (C6H5OH), bp=182oC + Chlorobenzene (C6H5Cl), bp=132oC
41
Procedure
1.
2.
3.
4.
5.
6.
7.
Set up a simple distillation apparatus with a 500-mL flask as
the still pot and a 50-mL graduated cylinder as the receiver.
Weigh the unknown. Place the sample in the flask using your
liquid funnel, then add about 100 mL of tap water, 40 mL of 6
M NaOH, and two or three boiling chips.
Heat the contents of the flask to a vigorous boil. when
distillation begins, make a record of the vapor temperature
vs. distillate volume.
Continue the distillation as long as oily material is
collected. If droplets of the oil remain in the condenser
and cling to the walls they may be flushed out by the
following procedure:
a.
Turn off the flow of cooling water through the condenser
jacket.
b.
Remove the rubber tube from the water tap and allow the
water to drain from the condenser jacket.
c.
Reconnect the tube to the water outlet, but do not turn
on the water yet. when steam begins to issue from the
lower end of the condenser, turn on the cooling water
again.
If it is not apparent from the vapor-temperature readings
that no more organic material is distilling, the following
test may be performed. Remove the receiver and collect a few
milliliters of the distillate in a small test tube, then
replace the receiver. Examine the liquid in the test tube
for the presence of oily drops. If none appear (distillate
is water only), the distillation may be stopped.
Read the volume of organic material in the graduated cylinder
as best you can and enter the value in your notebook.
Transfer the distillate to a separatory funnel and add about
50 mL of water. Do not shake! Allow the layers to separate,
and then draw off the organic liquid and weigh it. Return
the wet organic compound to your instructor in the same
container in which the unknown was received.
The Report
A brief discussion of the basic principles of steam
distillation should be followed by an account of your observations
and measurements. If your sample is considered to be an
"unknown," report the approximate volume of recovered compound.
The Experimental section should, of course, contain full details
of the method by which you carried out the steam distillation as
well as all relevant data. The Discussion of Results should
include some comment on the observed vapor temperatures and their
significance.
42
CHE-311
Report for Steam Distillation
1.
Include the normal heading.
2.
Discuss the basic principles of steam distillation.
3. State what you did in this experiment in one or two sentences;
be explicit.
4. Tabulate all relevant data.
chlorobenzene in the unknown.
Include the weight percent
5.
Discuss your data and observations.
6.
Questions:
See previous page.
a) What properties must a compound have in order to be steam
distillable?
b)
What properties do non-steam distillable compounds have?
c) What was the purpose of adding sodium hydroxide to the still
pot?
d) When would you use a steam distillation as a method of
separation and purification?
f) define Dalton’s Law and discuss how Dalton's Law is relevant to
steam distillation.
Answer questions 1, 2, 3 on pages 760-761 of your lab text.
43
EXPERIMENT: Recrystallization
Read p. 648-674 in your lab text!
This experiment offers a taste of organic preparative work
which includes a recrystallization as the final step. While you
have no prior experience and certainly would not, at this stage,
be expected to understand the chemistry involved in the reaction,
you can carry out the preparation if you follow directions.
The type of compound to be made is called an amide, which is
formed by the reaction of an amine with an acid anhydride (one of
several ways by which an amide may be prepared). The reaction is
represented by the following general equation:
RNH2 + (CH3CO)2O ----> CH3CONHR + CH3CO2H
amine
acetic
amide
acetic
anhydride
(substituted
acid
acetamide)
In the formula for the amide, the R represents any organic
group and NH2 is the amine group. The specific amide you are to
prepare is a derivative of the compound acetamide (CH3CONH2),
which is but one of the many compounds in the general class of
amides. Different amides can be obtained by using different
anhydrides or related reagents.
You will receive a sample of an "unknown" amine which is to
be converted to the corresponding amide following the general
procedure outlined below. The product of the reaction is then to
be purified by recrystallization. Identification of the purified
amide will be made by means of the melting point and mixturemelting-point determinations.
Procedure
Note: The type of amine to be used in this experiment has a
tendency to undergo oxidative changes in storage, resulting in the
formation of colored impurities. Most of the latter will be
removed during the reaction, and the final purification of the
product by recrystallization should eliminate any residual
impurity.
The reaction is a relatively simple one; it requires no
special apparatus and takes a relatively short time. The acetic
anhydride is added to the amine salt solution. However, the
anhydride will react only with the amine, and not with the salt
that was formed by dissolving the amine in the hydrochloric acid
solution. The acidic salt must therefore be neutralized to free
44
the amine, and this is accomplished by adding the sodium acetate
solution:
RNH2 + H3O+ + Cl- ---> RNH3+
base
acid
acid
+ Cl- + H2O
base
RNH3+ + Cl- + Na+ + C2H3O2- ------> RNH2 + HC2H3O2 + Na + Clacid
base
base
acid
A.
Reaction
Before carrying out the reaction, it is necessary to make up
a solution that will be needed in a later step. Dissolve 8 g
of sodium acetate trihydrate (NaC2H3O2  3 H2O) in 25 mL of
water in a small beaker and set aside.
1.
2.
3.
4.
5.
Prepare a solution of 5 mL concentrated hydrochloric acid in
125 mL water in a 250-mL beaker.
Weigh about 6 g of the liquid or solid amine into a 50-mL
beaker. It is not necessary to measure out exactly 6.00 g,
but the actual weight used should be recorded in your
notebook. If the amine is liquid, a clean medicine dropper
pipet may be used to transfer the compound from the vial to
the beaker.
Transfer the amine to a 500-mL Erlenmeyer flask. Rinse the
50-mL beaker with small portions of the dilute hydrochloric
acid you prepared, and add the rinsings to the flask. Pour
any remaining hydrochloric acid solution into the flask.
Swirl the flask carefully to dissolve the amine. Gentle
warming may be necessary, and some insoluble matter may
remain.
Carefully warm the solution of the amine in hydrochloric acid
on a hot plate or steam bath. Place a thermometer in the
solution, and when the temperature reaches 50-55oC, remove
the flask from the heat source.
Caution: In this step you are to add the reagent acetic
anhydride, which is both a lachrymator (induces the flow of
tears) and corrosive. The reagent must be handled carefully.
Should any of the liquid come into contact with your skin or
clothing, wash the affected area immediately with large
quantities of water.
Measure out 6 mL of acetic anhydride in a dry graduated
cylinder and carefully add the reagent to the warm acid
45
6.
7.
solution of the amine. Swirl the mixture gently until the
anhydride is completely dissolved.
Immediately add the sodium acetate solution you previously
made and set aside, and thoroughly mix the reactants by
swirling the flask. Allow the flask to stand for about 5
minutes, while occasionally stirring the contents.
Place the flask in an ice-water bath and stir the mixture
vigorously with a glass rod. Within a few minutes a solid
should separate from the solution. In some cases the product
initially appears as an oil, but this should be no cause for
concern at this stage. Allow the flask to remain in the
cooling bath for 15 minutes.
B.
Isolation and Preliminary Purification of Crude Product
1.
While the reaction mixture is cooling, arrange a suction
filtration apparatus. Be sure to clamp the flask to a ring
stand or other support. Place a disk of filter paper in the
funnel and moisten the paper with water.
Filter the crude product through the Buchner funnel. Rinse
the Erlenmeyer flask with small quantities of ice-cold water
to remove any solid that sticks to the walls.
2.
3.
C.
Note: If the product separated as an oil and did not
solidify after standing in the ice-water bath, carefully
decant as much of the supernatant liquid as possible.
Add a
few grams of crushed ice to the oil in the flask and stir the
mixture vigorously while cooling the flask in the ice-water
bath. If the oil does not solidify, add about 20 mL of
water, shake the mixture, and let it stand for a minute or
two. Carefully decant the upper aqueous layer and repeat the
treatment with ice, with somewhat longer cooling periods in
the ice-water bath, until solidification occurs.
Leave the crude solid in the Buchner funnel and wash the
filter cake with 50 mL of ice-cold water. Resume the suction
for about 5 minutes.
Purification
The amides may be recrystallizable from a number of different
solvents, including water. Unless you are instructed otherwise,
the solvent selection in this situation is restricted to water,
methanol, and ethanol. Some of the amides that were prepared can
be crystallized from one of these solvents, while others may
require a mixed system (water plus either methanol or ethanol).
If it is known that a crude product is to be recrystallized
from water or a water-miscible organic solvent, then it is not
necessary that the solid be absolutely dry before carrying out the
46
purification. Such is the case in this preparation. (On the
other hand, if there is a possibility that a solvent which is not
itself soluble in water will be needed, then steps must be taken
to remove the residual water from the crude product.)
1.
2.
Selection of the solvent: try water first, followed by
methanol and then ethanol, using fresh samples of crude
in each case. If it is found that the solid is not
sufficiently soluble in water, but too soluble in both
of the alcohols, then it is necessary to try the mixed
solvent approach.
Recrystallize the crude product following the general
directions given below:
Recrystallization.
1. Select the appropriate solvent for recrystallization.
Sometimes you can find data on solubility for your compound or
related compounds in the CRC Handbook or in the chemical
literature. Test one or more possible solvents using small
amounts in test tubes. The compound you are trying to
recrystallize should be insoluble in the cold solvent, dissolve in
the solvent when heated, and recrystallize when the solvent is
cooled. A mixed solvent may be required.
2. On a hot plate, heat some of the solvent you have selected in
an erlenmeyer flask. Put the impure, solid compound in a beaker.
Placing the beaker on the hot plate, quickly add a small amount
of the hot solvent. If the compound does not completely dissolve,
add additional small amounts of the solvent until complete
dissolution is achieved. You want to use a minimum of the hot
solvent to dissolve the compound. Do not needlessly boil off the
solvent; if the compound is going to dissolve it will do so in a
few seconds.
3. Once the impure compound is totally dissolved you must decide
whether to decolorize or not. If necessary, add a small amount of
decolorizing carbon to the hot solution. Place your stemless
glass funnel in the top of a beaker. Fold a fluted filter paper
(page 46 of your lab text) and place it in the stemless funnel.
Add a few mL of the pure solvent to the beaker. Put the hot
filtration assembly on the hot plate and add the hot, decolorized
solution of your compound to the filter. The purpose of the
stemless funnel, beaker, and hot plate is to keep the compound to
be purified in solution while you filter out the carbon.
4. Let the hot solution cool to room temperature on the bench
top. Then use an ice-water bath to cool the solution even more.
47
If crystallization does not begin, try scratching the wall of the
beaker with your glass rod.
5. Vacuum filter the cooled solution to recover the
recrystallized solid. You may want to wash the compound with a
small amount of cold solvent if the compound is not too soluble in
the cold solvent.
6. After air drying for a couple of days you can weigh and take
the melting point of the purified compound before packaging it.
D.
Identification
When the product is completely dry, you are to determine the
melting range. Positive identification can be made by means of
the mixture-melting-range determination. Until this can be done,
put your dry purified product in a clean, dry, wide mouth bottle
or vial of appropriate size (the bottle should be at least half
full), which has been weighed while empty. Reweigh the bottle
plus contents to obtain the net weight of product, and record this
information in your notebook.
After you have determined what the compound is, label the package
as indicated below, or as directed by your instructor.
Your name
Name of compound
Observed melting range
Net weight
Date
You will turn in the product with your lab report.
Interpretation of Results and the Report
The experiment involved both the preparation and purification
of an organic compound. The primary objective was the
purification of the product by recrystallization, and so very
little need by said about the chemistry of the preparative
reaction. Greater emphasis should be placed on the determination
of the best solvent system and the results of the purification
process in terms of percentage recovery. Because identification
of the compound by the mixture-melting-point technique is
required, the actual writing of the report must be deferred until
that operation is completed. A qualitative statement about the
degree of purity as estimated from the observed melting range and
comparison with the literature value is also in order. The
Experimental section should, of course, provide complete details
on the method that you actually followed.
48
Purified Substituted Amide
In the experiment, you prepared a substituted amide from an
"unknown" amine. The melting range determination will indicate
how pure your product is, and the identity of the compound may be
verified by the mixed-melting-point method.
1.
Determine the melting range of your product.
2.
Refer to table on the next page, which lists the melting
points of a number of amides, including the compound you have
made. Select those which have melting points close to the
range you determined for your product. Use a mixturemelting-point determination, employing authentic samples of
the amides that may be identical to your compound, to find
out which amide you prepared (Notes 1 and 2).
Notes
1.
2.
Even if you find that the first mixture tested shows no
depression of the melting point, you still must carry out the
mixture-melting-point determinations with the other
possibilities in order to eliminate them with certainty.
The actual melting points of the authentic samples may not
coincide with the literature values because the samples may
not be 100% pure. The samples may nevertheless be utilized
for the purpose intended. Do not measure the melting range
of any of the standards, but accept the literature values
given in the tables or listed on the container labels.
Melting Points
of Some N-Substituted Acetamides
Amide (CH3CONHR)
m-chloroacetanilide
o-ethoxyacetanilide
o-methoxyacetanilide
o-chloroacetanilide
o-methylacetanilide
o-ethylacetanilide
acetanilide
2,4-dimethylacetanilide
p-methoxyacetanilide
2,3-dimethylacetanilide
p-ethoxyacetanilide
2,5-dimethylacetanilide
p-methylacetanilide
m-nitroacetanilide
mp (oC)
78
78
58
87
110
111
114
130
130
135
137
139
153
155
49
Interpretation of Results and the Report
The results of the mixture-melting-point determinations
should be presented in tabular form. List all of the
possibilities tested and the corresponding measurements in such a
way that your conclusions are obvious from your experimental
results.
50
CHE 311
1.
Report for recrytallization/mp determination
As before:
name
date
CHE 311-0x
unknown #
2. In your own words, explain what recrystallization is and how
it works to separate solid compounds. Describe how the
appropriate solvent is selected for recrystallization.
3. In a few sentences, summarize what you did in this experiment,
be specific.
4.
Write balanced equations for the reactions.
5.
Make a table:
weight of the unknown
g
weight of product
g
observed melting range of unknown amide
list of possible compounds and their literature
mp's, and the observed mixed mp's with your product.
6. Conclusion as to the identity of the product amide and unknown
amine? Justify your answer.
7.
How pure do you think the product is? Explain?
8.
Answer the following questions:
a) For the following reported melting points, comment on the
purity of the sample:
i) 78-89 oC
ii) 299-301 oC
iii) 178 oC decomposes
iv) 137-139 oC
51
b) If,
comes out of
What can you
discussed in
in any recrystallization, an "oil" (liquid phase)
solution rather than a solid, why did this happen?
do about it? Please note that although this is
your lab text, the answer is not correct!
c) What happens in this experiment if more than the minimum
of hot solvent is used in the recrystallization?
d) Based on the structure of the now known amine and amide,
calculate the % yield of your product.
Note:
% yield = (actual yield / theoretical yield) * 100%
You will have to convert to moles and use the balanced equation to
calculate theoretical yield!
e) What was the purpose of the hot filtration?
you use gravity or suction filtration at this point?
f)
Why didn’t
Questions on page 664 of your lab text: 1, 2, 3, 4.
g) In the CRC Handbook, look up 1-bromo-2-nitrobenzene (look
under benzene) and list the mp, crystal form, and the solvent used
in the recrystallization of this compound.
9.
Attach the blue carbons from your notebook.
10. Package, label and turn in your product. name, date, contents,
weight, mp or bp, %yield.
52
CHE-311
Chromatography
chromatography ("colored writing")
separations based on differences in absorption on a
stationary phase and differences in solubility in a
moving phase.
I.
Thin Layer Chromatography (tlc)
stationary phase = thin layer of solid silica gel, alumina,
etc.
moving phase =
liquid solvent (capillary action)
+---------+
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
mark--> +
o
¦
¦
¦
+---------+
+---------+
mark--> +---------¦
¦
o
¦
¦
¦
¦
o
¦
¦
o
¦
¦
¦
¦
¦
+
¦
¦
¦
+---------+
-----------------------¦
+---------+
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
+---------¦
¦
¦
¦
o
¦
¦
¦
¦
¦
¦
¦
¦
o
¦
¦
¦
¦
o
¦
¦
initial ¦
+
¦
¦
spot
+----+---------+---¦ solvent
+------------------+
¦
¦
¦
¦
¦
¦
¦
¦
x1¦ x2¦ x3¦
y¦
¦
¦
¦
¦
------------------
distance component traveled
Rf = retention factor = ----------------------------distance traveled by solvent front
Rf1 = x1/y;
Rf2 = x2/y;
etc.
53
application:
II.
a)
analysis of mixture : number of components
(solids & non volatile liquids)
b)
separation of mg amounts
c)
identification
(Rf's or direct comparison)
Column Chromatography
stationary phase = column of solid silica gel, alumina,
etc.
moving phase = liquid solvent
¦
¦
¦
¦
solvent->¦
¦
¦
¦
+---¦
¦
¦
absorbent->¦
¦
¦
¦
¦
¦
+---¦
+---+
+---+
¦
column preparation
loading the mixture
development
collection of fractions
analysis of fractions
(tlc)
fractions
+----¦
¦
¦
+----+
+----¦
¦
¦
+----+
¦
¦
+----¦
+----+
applications:
a)
analysis of mixture
(solids and liquids)
b)
separations of 0.1 gram quantities
¦
¦
¦
¦
+----+
54
III.
Gas Liquid Chromatography
(glc)
stationary phase = column of non volatile liquid (carbowax,
DNP, SE-30, etc.) on solid support.
moving phase = gas
Oven
Recorder
+------------------------+
+----------+
¦
¦ +-------¦
¦
+---¦
+-+ +-+ +-+ +-+
+---+
¦
¦
injection¦
+--+ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ +---¦
+
¦ +------+ ¦
+---¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦ ¦
+---+
+-¦
+-+
¦ ¦ +-+ +-+ +-+ +-+ +-+
¦ detector ¦
¦
¦ ¦
¦
¦
¦
¦ ¦
¦
¦
¦
¦ ¦
¦
+------+
¦ +------------------------+
¦
Gas
Gas Chromatograph:
+----------------------------------------------+
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
¦
+----------------------------------------------+
distance after injection
retention time = --------------------------chart speed
%A
=
area A
area A
------------------------------ X
area A + area B + area C + etc.
=
height X width (at half height)
100%
55
applications:
IV.
a)
analysis of mixture, # of components
(volatile liquids or gases)
b)
separation of mg samples
c)
identification
d)
per cent composition
(retention time)
Today's experiments:
1.
tlc
do tlc on your unknown on both silica gel and alumina.
use each of the two solvent systems.
2.
glc
glc on known 50/50 mixture of alcohol and ketone
glc on pure alcohol
glc on your unknown mixture of alcohol and ketone
56
EXPERIMENT: Thin-Layer and Column Chromatography
Read 792-807 in your lab text!
The following experiments include both thin-layer and column
chromatographies that are based solely on the adsorption process.
The main intent is to familiarize you with the techniques. Once
you have learned the basic idea and procedure, you will be in a
position to utilize one or both of these methods if you occasion
arises during your later experiences with the preparative
experiments.
You will obtain an "unknown" mixture consisting of a minimum
of two solid compounds; one or more of the components may be
colorless. a sample is to be subjected to thin-layer
chromatography to determine the number of components and their Rf.
(The same mixture could then be chromatographed in a column in an
effort to separate and recover the individual compounds. Progress
of the column chromatography could to be determined by thin-layer
chromatography of each eluate fraction. You might also evaporate
each eluate that is known to contain dissolved solid and determine
the melting range of the residue; a comparison with the melting
range of the original mixture would then be done.) It is quite
possible that you will not achieve a complete separation by column
chromatography because (a) the solvent system that is specified is
not the best, (b) an insufficient number of eluate fractions are
collected, (c) the adsorbent is not the optimum choice, or (d) the
column is not long enough. Nevertheless, exposure to the method
will provide experience in carrying out the chromatography and may
well point up some of the difficulties that can be faced. If
there were enough time, it is very probable that you could work
out the optimum conditions for separation of your sample.
A.
Thin-Layer Chromatography of the Original Mixture
The effectiveness of two different adsorbents, silica gel and
alumina, will be compared using two solvent systems.
Procedure
1.
Obtain a 5- or 10-mL beaker or a vial of similar capacity,
two TLC strips coated with aluminum oxide, and two TLC strips
coated with silica gel. Use a sharp pencil to carefully mark
the top of each strip (e.g., A and S, respectively) so that
they can be distinguished.
57
2.
3.
4.
5.
Place about 10 mg (estimated; do not weigh!) of the solid
mixture in the small container and add about 1 mL of acetone
to dissolve the sample.
Spot the solution on each of the strips. Mark the top of one
alumina strip 1:1 and the other 1:3; do the same to the
silica gel strips.
Develop the silica gel chromatograms using ethyl acetatecyclohexane (1:1) for one and 25% ethyl acetate-75%
cyclohexane (1:3) for the other. Develop the alumina strips
in the same way. Note: Ethyl acetate alone is too polar and
cyclohexane too nonpolar. One or both of the specified
solvent mixtures may prove to be satisfactory, or neither may
be the most desirable solvent system. A different single
solvent or combination of solvents may be superior, but for
expediency you are restricted to the two solutions indicated
above.
Follow the instructions given. (Note that the solvent moves
more slowly through the alumina then it does through silica
gel.)
Calculate Rf values for all observed spots.
The Report
The introductory section should include the usual background
discussion of the theoretical principles underlying the
procedures, as well as a statement of the problem. Be sure to
include all observations and measurements (Rf values) in the
Experimental section. All thin-layer strips should be taped or
stapled to a sheet of paper and attached to the report.
The discussion of results should provide a comparison of the thinlayer chromatographies on alumina and on silica gel and the two
solvent systems. In the event that you did not obtain a complete
separation of components, offer some possible reasons therefore
and some suggestions as to how separation could be done more
effectively if you were to repeat the attempt.
58
Che 311
Chromatography reports
You will submit two reports for the chromatography experiments,
one for tlc/column and one for glc. Both of these reports will be
due two weeks from today.
Thin Layer and Column Chromatography.
1.
Include the regular heading.
2. Explain in your own words what chromatography is and how it
works; with emphasis on tlc and column.
3. In a few sentences state what you did in this experiment; be
specific.
4. Make a table showing the Rf values for each component for each
adsorbent and each solvent system you used in the tlc.
5. Which adsorbent would you select for a column chromatography
separation of your unknown and why? Which component would elude
from the column last?
6.
Discuss the results of your experiment.
7. Staple or tape all of the tlc strips to a piece of paper and
label each one. This will be included as part of your report.
8. Answer questions:
a) Two components, A and B, were separated by tlc. When the
solvent front had moved 10.0 cm above the level of the original
spot, the spot corresponding to A was 3.5 cm and that of B was 4.1
cm above the original spot. What are the retention factors for A
and B? Which component would elude first from a column
chromatography using the same absorbant and solvent?
b) Describe how thin layer chromatography could be used to
analyze a urine sample for the presence of cocaine if you had a
known sample in the lab.
c) Why is it important that the sample to be analzed by tlc be
dry?
d) Why must the solvent level be below the original spot on the
tlc plate?
e) Why must the cap be in place on the bottle during the tlc
separation?
Answer questions 1, 2, 3, 4 on page 807 of your lab text.
9.
Attach the carbons from your notebook.
59
Gas-Liquid Chromatography
EXPERIMENT: Analysis of Alcohol-Ketone Mixtures
Read p. 808-823 in your lab text!
A ketone is a type of organic compound that is represented by
the general formula I; it is related to another kind of compound,
a secondary alcohol (II).
I.
R-C=O
|
R’
II.
R-C-OH
|
R’
A ketone can be made from the corresponding alcohol by oxidation;
conversely, reduction of a ketone results in the formation of the
secondary alcohol. (You need not be overly concerned with the
chemistry of these substances now. The relationships just
described will be amplified at the appropriate point later in the
course.)
When a ketone is prepared from the alcohol, or vice versa, it
is possible that not all of the starting material is converted to
the end product. The final product may therefore be contaminated
with some of the starting material. The difference between the
boiling points of the alcohol and the ketone becomes smaller as
their molecular weights increase, making it more difficult to
separate them by conventional distillation procedures. Analysis
by GLC, however, readily indicates the presence of the
contaminant.
You will receive a mixture of a ketone and the corresponding
secondary alcohol. Carry out a GLC analysis following the general
instructions given and whatever special instructions are provided
for the instrument available in your laboratory. You will also
need to measure the chart speed (inches/minute or cm/min).
If your sample was given to you as an "unknown," compute the
approximate percentage composition by measuring the areas of
the peaks. If authentic samples of the various possibilities
are available, attempt an identification of the components of
your mixture. In this case, you need use either an authentic
ketone or alcohol, but not both.
60
Gas Chromatography Report
1.
Include the regular heading.
2. Explain in your own words the physical basis for gas
chromatography and how it works to separate and purify compounds.
3. State in a few sentences what you did. Be sure to give
information about the column(s) used and the temperature(s).
4.
Make a table:
stationary phase:
column temperature:
carrier gas:
detector:
4-methyl-2-pentanol retention time =
Known:
retention
time (sec)
height
(units)
width-1/2h area
calculated
(units)
(units) weight %
4-methyl2-pentanol
4-methyl2-pentanone
Unknown:
retention height width-1/2h
time (sec) (units) (units)
area
(units)
calculated
weight %
4-methyl2-pentanol
4-methyl2-pentanone
5.
Discuss the results of your experiment.
6.
Attach the chromatograms that you ran, suitably labeled.
(show your calculations!)
7.
Attach the notebook carbons.
61
8.
Answer the following questions:
In a glc three peaks are observed and their areas are
calculated as follows: A, 13.5 mm2; B, 20.2 mm2; C, 4.6 mm2. What
is the % composition of each component in this mixture?
Describe how the identity of each of the components could be
determined if known samples of two of the compounds were
available.
In the known 50%/50% mixture of alcohol and ketone, why are
the areas of the two peaks not equal?
Page 823 of your lab text:
problems 1, 2, 4.
62
CHE 311
Preparative reaction pre-labs
For all preparative reaction lab experiments you will have to
submit a pre-lab writeup as well as the usual post-lab report.
The pre-lab is due at least 24 hours before the lab. Failure to
submit the pre-lab will result in your not being allowed to begin
the synthesis in lab.
For the first preparative experiment, prepare the pre-lab in your
notebook (the carbons should be submitted prior to the lab; turn
them into my mailbox in the Chem. Office, NSM B-202).
The pre-lab should include the following:
1. A balanced equation for the reaction as you are going to carry
it out.
2. A table of the physical properties (see lab handout) of the
reactants/solvents and products. (a copy of the CRC is in the
reserve book room and there is one in the lab)
3. A step by step procedure for the reaction as you are going to
carry it out.
CHE-311
Syntheses of Alyl Halides
In this experiment you will synthesize two alkyl halides, a
primary bromide (1-bromobutane) and a tertiary chloride (2-chloro2-methyl-butane). You will have two weeks to complete both
syntheses. The first lab period you will begin the synthesis of
1-bromobutane; once the reaction mixture is refluxing, you will
start the synthesis of 2-chloro-2-methylbutane. Both syntheses
will be finished during the second lab period.
Note: you must submit prelabs for both syntheses prior to the
start of the lab!
See pages 204-211 in your text.
63
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
fw
Moles
weight
(g)
volume
(mL)
sodium bromide
103
0.17
17.0
--
water
18
0.94
17
1-butanol
74
0.109
sulfuric acid
98
(HBr)
81
calcium chloride 183
(anhyd.)
density
(g/mL)
bp
mp
solubility
--
1390
755
sw, sls al
17
1.00
100
0
8.1
10
0.81
117
-89
0.26
25.8
14
1.84
338
10
(0.17)
(13.8)
--
--
-67
--
--
--
--
--
-sw,sal
sw,d al
-88.5 sw,sal
568
I ace; s eth
Product(s)
1-bromobutane
137
(0.109)
(14.9)
NaHSO4
120
(0.109)
(13.1)
water
18
(0.109)
(2.0)
(11.7)
-(2.0)
1.28
102
--
d
1.00
100
(theoretical)
CH3CH2CH2CH2-OH
+
NaBr
+
H2SO4
--->
CH3CH2CH2CH2-Br
+
NaHSO4
+
H2O
-112 iw,sal
>315 sw,sls al
0
--
64
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
Product(s)
fw
Moles
weight
(g)
volume
(mL)
density
(g/mL)
bp
mp
solubility
65
Report for syntheses of 1-bromobutane
1.
name
Balanced equation for reaction as you carried it out:
2. Step-wise mechanism for the reaction. Use curved arrow
formalism and label the RDS. Show how each product is formed if
more than one product is possible.
Use additional paper if
necessary. Give the name of the mechanism.
3.
weight of the starting material
moles of alcohol
weight of the product halide
moles of product
% yield
boiling point (range) of the product
literature values for the bp of the
expected product(s)
4.
Discussion of results.
66
5.
a) Why did you wash the crude product with 2M NaOH?
b) Why did you then wash it with water?
c) Why was the 1-bromobutane treated with anydydrous
magnesium sulfate?
d) State two purposes of the simple distillation of the
product?
e) Was the product produced by an Sn1 or an Sn2 mechanism?
How could you verify this?
f) What role did the sulfuric acid play in this experment?
Explain! equations!
Answer questions 1, 2, 3, 5, 6 on p. 210-211 of your lab
text.
6. Attach the carbons from your notebook, the pre-lab carbons,
and table of physical properties. Label and turn in your product.
67
Report for syntheses of 2-chloro-2-methylbutane
name
1.
Balanced equation for reaction as you carried it out:
2. Step-wise mechanism for the reaction. Use curved arrow
formalism and label the RDS. Name the mechanism! Show how each
product is formed if more than one product is possible.
Use
additional paper if necessary.
3.
weight of the starting material
moles of alcohol
weight of the product halide
moles of product
% yield
boiling point (range) of the product
literature values for the bp of the
expected product
4. Discussion of results. Be sure to compare the synthesis of 1bromobutane with that of 2-chloro-2-methylbutane.
68
Include a table showing the following for the syntheses of n-butyl
bromide and for tert-butyl choloride:
time of reaction
temperature of reaction
catalyst
%yield
class of alcohol
mechanism
5.
a) Draw all of the isomeric butanols.
of decreasing reactivity with conc. HCl.
Number them in order
b) Why did you wash the crude product in this experiment with
aqueous sodium bicarbonate?
c) Why didn't you wash it with aqueous NaOH?
d) Why were you able to wash the crude 1-bromobutane with
NaOH?
e) What is one major disadvantage of washing with sodium
bicarbonate?
f) Neopentyl alcohol reacts with conc. HCl to produce tertpentyl chloride. Outline all steps in the mechanism to show how
this product is formed.
g) Why does 1-pentanol produce only 1-bromopentane and not 2bromopentane when reacted with HBr?
h) Solid sodium hydroxide is a drying agent. Why did we not
use it in place of magnesium sulfate when drying the crude
product?
i) What were the two purposes for the simple distillation at
the end of this synthesis?
Answer questions 2, 3, 4, 5 on page 211 of your lab text.
6. Attach the carbons from your notebook, the pre-lab carbons,and
table of physical properties. Label and turn in your product.
69
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
Product(s)
fw
Moles
weight
(g)
volume
(mL)
density
(g/mL)
bp
mp
solubility
70
name
Report for dehydration of 4-methylcyclohexanol
1.
Balanced equations for the reactions as you carried them out:
2. Step-wise mechanism for the reaction. Use curved arrow
formalism and label the RDS. Name of the mechanism?
3.
weight of the limiting reagent
moles of limiting reagent
weight of the product
moles of product
% yield
boiling range of the product
literature value for the bp of the
expected product(s)
71
4.
How pure is your product?
5.
Discuss your results.
How do you know?
6.
a) Predict the product(s) for the dehydration of 3-methyl-2butanol.
b) Predict the product(s) of the dehydration of each of the
following alcohols: 1-butanol, cyclohexanol, 1methylcyclohexanol, 2-methylcylcohexanol, neopentyl alcohol, 4methyl-1-pentanol.
7. Attach the carbons from your notebook, the pre-lab carbons.
Don't forget to label and turn in your product.
72
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
Product(s)
fw
Moles
weight
(g)
volume
(mL)
density
(g/mL)
bp
mp
solubility
73
CHE 311
Nitration of a halobenzene
This will be your third preparative experiment.
pre-lab writeup is due 24 hours before the lab.
Remember that the
Notes:
1.
Use your largest Erlenmeyer flask as the reaction vessel.
2. Include a magnetic stirrer in the apparatus. Leave roon
between the bottom of the flask and the top of the stirrer base
for insertion of a plastic bowl (water bath).
3. Wear rubber gloves to protect your hands, not only
against the concentrated acids, but also the product which is a
skin irritant.
4. If two or more products are expected (e.g. as from
chlorobenzene), calculate the theoretical yield of the mixture as
if it were a single substance. Calculate the percent yield of the
actual product as if it were exclusively formed.
You will use 0.1 mole of the following halobenzene as the starting
material:
desk number
1,10,20,4
bromobenzene
6,16,11
chlorobenzene
2,12,22,9
1,4-dichlorobenzene
7,17,21
1,4-dibromobenzene
3,13,23,19 1,3-dichlorobenzene
8,18,14
1,2-dichlorobenzene
5,15,24
1-bromo-4-chlorobenzene
74
Nitration of a Haloarene: Experimental Procedure
The starting haloarenes for this synthesis are either liquid
or solid, but the desired product in each case is a solid. For
some, only one possible product may be formed; some may react to
form a mixture of two products, one of which predominates. The
remaining compounds may theoretically be converted to a mixture of
two or more products. Included in your assignment is the
isolation and determination of the identity of the major product.
A.Apparatus
The standard-taper assembly described below could be used for
this preparation. However, it is also possible to carry out the
procedure in an Erlenmeyer flask (which you will do) but it is
necessary to carry out the reaction in a fume hood.
1.
A 500-mL Erlenmeyer flask will serve as the reaction vessel.
The thermometer is placed in the flask, with its bulb
resting on the bottom. When you must stir or shake the
reaction mixture, hold the thermometer in place by grasping
the neck of the flask and the thermometer simultaneously with
one hand.
[alternatively:
a. Fit a 250-mL two-neck flask with a Claisen adapter or use a
500-mL three-neck flask. If you are provided with a magnetic
stirrer, place a magnetic stirring bar in the flask.
b. Place a thermometer in the angled side neck of the flask and
position the bulb so that it will be immersed in the reaction
mixture. Attach a reflux condenser to the other side neck
and connect the top opening of the condenser to a gas trop
(oxides of nitrogen may be evolved).
c. Attach a dropping funnel to the center neck if the compound
to be nitrated is a liquid. If your starting material is a
solid, the center neck is to be plugged with a glass
stopper.]
2.
Surround the flask with a plastic bowl containing some tap
water. Obtain some crushed ice in a separate container and
keep it handy for cooling the reaction mixture as needed.
B.
Reaction
3.
Begin the preparation of the nitrating agent by pouring 20 mL
(28.5 g; 0.32 mole) of concentrated nitric acid through a
narrow-stem funnel into the flask. Do not use the addition
funnel, if one is included in your assembly. Carefully add
75
in small portions of 20 mL (37 g; 0.36 mole) of concentrated
sulfuric acid. Stir the mixture mechanically or swirl the
flask by hand while you are adding the sulfuric acid. When
all of the sulfuric acid has been added, cool the mixture to
25-30oC by adding some ice to the water bath, if necessary.
Do not cool the solution below 25oC.
If the temperature of the nitrating agent is allowed to fall much
below 25oC it is possible that insufficient energy will be
available to initiate the reaction. Continued addition of the
substance to be nitrated will permit the concentration of
unreacted starting material to build up. when the reaction does
begin, and heat is evolved, all of the aromatic compound present
may interact with the nitrating agent and the reaction may get out
of control because of the excessive evolution of heat.
4.
Measure out a quantity equivalent to 0.1 mole of the starting
material you were assigned. Add the aryl halide to the
nitrating agent as directed below. Stir or swirl the
reaction mixture to mix the reactants thoroughly. Use the
cooling bath to control the temperature so that it does not
rise above 60oC, but do not allow the temperature to fall
o
below 30 C. If the temperature does get too low, remove the
cooling bath temporarily and allow the reaction mixture to
warm up before continuing the addition.
5.
6.
Continue to add the starting material in the manner described
above until all of it is consumed.
When the temperature of the reaction mixture no longer rises
spontaneously, heat the mixture on a steam bath or hot water
bath for 30 minutes. A heating mantle may also be used, but
be certain to wipe the outside of the flask first to remove
any adhering water. Heat the mixture to a temperature
between 60 and 100oC.
7.
Remove the flask from the heat source and allow the mixture
to cool to room temperature. You may help it along by using
a cooling bath.
C.
Isolation and Preliminary Purification
8.
Put a mixture of 150 mL of water and enough crushed ice to
bring the volume to 200 mL into a 400- or 600-mL beaker.
Carefully pour the contents of the flask into the cold water
while stirring the mixture with a glass rod. Rinse the
76
9.
10.
D.
reaction flask with a small amount of ice water and add the
rinsings to the beaker.
The crude product should separate as a solid. If it does so,
it can be isolated by suction filtration. If the crude
product separates from the aqueous phase as an oil, the
following measures may be taken.
a.
Carefully decent as much of the aqueous phase as
possible, leaving the oily material behind. Add some
crushed ice and vigorously stir the mixture with a glass
rod. If this treatment does not effect solidification
of the material, see step b (below).
b.
Dissolve the crude oily product in about 50 mL of
diethyl ether or dichloromethane by adding the solvent
directly to the beaker that contains the product-water
mixture. Transfer the contents of the beaker to a
separatory funnel and separate and discard the aqueous
phase. After completing step 11, continue with step
12b.
The reaction mixture contained a strongly acidic solution,
some of which will remain admixed with the crude product.
The product must therefore be washed thoroughly with water.
A solid may be washed while it is in the Buchner funnel; a
product in solution should be washed in a separatory funnel.
Purification
11.a.
b.
The product is a solid, so a recrystallization is in
order. Select a recrystallizing solvent from among
those available to you in the laboratory.
If the crude product was dissolved in an organic
solvent, that solvent must be removed at this point. A
rotary evaporator would be best for this purpose, but
any other suitable means may be employed. If the
residue is still liquid, it may still be subjected to a
crystallization procedure, just as if it were solid.
E.
Verification of Identity and Purity
12.
13.
Determine the melting range of your product.
The product will be analyzed by thin-layer chromatography on
silica gel, with the eluting solvent 9:1 (v:v)
hexane:chloroform. Pure samples of most of the possible
reaction products are available, you should attempt an
identification by comparison of Rf values for the authentic
14.
material(s) run alongside the reaction product on the same
TLC strip.
Package the product and turn it in.
77
The Report
The Introductory section of the report should include a
discussion of the reaction mechanism. A description of the intent
of the experimental work, naming the specific compound to be
nitrated, and a description of the anticipated outcome should
precede the Experimental section and the Discussion of Results.
In the latter, be sure to interpret the experimental results
(including spectra) and to state conclusions about such steric and
inductive effects as are applicable.
78
Report for nitration of a halobenzene
name
1. Balanced equation for the reaction as you carried it out:
2. Step-wise mechanism for the reaction. Use curved arrow
formalism and label the RDS. Name of the mechanism? Show how
each product is formed if more than one product is possible.
Use
additional paper if necessary.
3.
weight of the limiting reagent
moles of limiting reagent
weigt of the product
moles of product
% yield
melting point (range) of the product
literature values for the mps of the
expected products
(name of each!)
79
tlc:
substrate
solvent
identity (if possible for each spot)
rf for each spot
4. What products did you expect this reaction to form? Explain
the effect that the group(s) present in the starting material have
on reactivity and orientation in this reaction and why. How many
were actually formed? What evidence do you have for this? How
did you identify them? If the number formed is different from the
number expected, explain.
5.
How pure is your product?
How do you know?
6.
Discuss your results further.
7.
a)In the nitration of bromobenzene, the product after
purification by recrystallization contains mostly the parabromonitrobenzene and little of the ortho-isomer. Explain.
b) Bromo is a deactivating group in EAS but an ortho/para
director. Use resonance structures to explain why no detectable
amounts of the meta isomer are obtained.
8. Attach the carbons from your notebook, the pre-lab carbons,
and the tlc. Don't forget to label and turn in your product.
80
CHE-311
Information for Final Exam
This exam is 20 questions long and consists of short essays
and a few calculations (bring your calculator).
To study for this exam, go over each of the techniques that
you have learned for separating and purifying organic compounds.
You are expected to know the terminology and basic physical
principles behind each method and technique. Know which methods
you should use under which circumstances. You should also look at
each of the preparatory experiments and know why you did each of
the operations that you did.
Calculations that you should be capable of doing include:
partition coefficient in extractions
Rf
retention times
% in gas chromatography
% yield
81
CHE 312 Organic Chemistry II
Instructor:
Office:
Phone:
e-mail:
Office hours:
Text:
1.
Dr. James L. Lyle
NSM D-323
(310) 243-3388, (310) 243-3376
jlyle@csudh.edu
TBA; open door policy.
Organic Chemistry, 6th Edition, Morrison & Boyd.
Study Guide for...
Model kit
Grading:
Traditional letter grades will be assigned. A = 100-93%,
A- = 92-90%, B+ = 89-88, etc.
Daily exams
=
100
4 exams @100 pts
=
400
final exam
=
100
600
2.
Exams.
No make up exams will be given.
3.
Final exam. The final exam will be will be comprehensive.
4.
Homework.
Homework is very important to doing well in this class and
mastering organic chemistry. Homework is not going to be
collected, but it should be done on a regular basis. Suggested
problems are attached. Many of these problems are lengthy. You
should be selective in which ones you do. If you have any
questions, see the instructor.
5.
Office hours.
The instructor is available at any time outside of class for
questions, etc. Do not hesitate to seek help if there is anything
you do not understand!
6. Prerequisite. Completion of the first semester of Organic
Chemistry, lecture and laboratory. Corequisite is enrolment in
CHE-313.
7. Academic Integrity. Please review the statement on Academic
Integrity in your University Catalog. Cheating will not be
tolerated.
82
8. Course goals, objectives and requirements are covered in the
rest of this syllabus.
9. Attendance is expected. Two of the daily exams scores will be
dropped to allow for unavoidable absences.
83
CHE-312
meeting
1.
2.
3.
4.
5.
6.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
45.
TENTATIVE SCHEDULE
Spring '03
date
subject
text
1/27
1/29
2/3
2/5
2/10
2/12
2/17
2/19
2/24
2/26
3/3
3/5
3/10
3/12
3/17
3/19
3/24
3/26
3/31-4/4
4/7
4/9
4/14
4/16
4/21
4/23
4/28
4/30
5/5
5/7
5/12
5/14
TBA
Infrared Spectroscopy
Nucl. Mag. Resonance
17.1,17.3-17.7
17.9-17.13,17.22
Aldehydes & Ketones
18
no class
EXAM I
Carboxylic acids
Functional derivatives
19
19/20
Carbanions I
21
Carbanions II
Michael Addition
EXAM II
Amines, syntheses
25
27
Spring Break, no class
Amines, reactions
Phenols
Aryl halides
EXAM III
Molecular Orbitals
Polynuclear Aromatics
Heterocyclics
Carbohydrates
EXAM IV
FINAL EXAM
22
23
24
26
28
30
34
84
CHE-312
HOMEWORK ASSIGNMENTS
Athough homework is not required to be turned in, it is required
that you do it. You will not pass this course if you do not
conscientiously do the homework assignments. Some of the
following problems have multiple parts. It may not be necessary
to do every part, but you should be able to do any homework
problem, or problems similar to them, on the exams. The answers
are in the Study Guide and should be consulted. You should also
do the homework on a regular basis after every lecture. There is
too much to do and learn if you put it off. If you have any
questions see the instructor.
Subject
Assignment
IR:
please note that in some later printings
Of the text the problems in this chapter
are off by .1; 17.2 (which starts What
is... ) may be 17.3 in your text,
17.3 (which starts give the... ) may be
17.4, etc., 17.5.
(Note: spectra are analyzed at the end of
the Study Guide.)
Handout.
nmr:
17.8(a-f),17.11,17.13,17.12,17.15,17.16,17.29,
p. 643: 1(a thru i).
aldehydes
& ketones
p. 701: 1,2, outline syntheses of each of the
compounds in problem 2 using as many methods as
possible for each from your choice of starting
materials.
p. 702: 3,4,5,18.16,6,10(a thru h).
p. 706: 30,32,33.
Outline all steps in the mechanisms for
nucleophilic addition and acid catalyzed nucleophilic addition. Which mechanisms go with
which reactions of aldehydes & ketones?
carboxylic
acids
p. 747: 1,2,3,4,6,7,13,15(a,b,c),27.
func. deriv.
p. 787: 1,2,3,4,5,6,7,20,21.
Outline all steps in the mechanisms for nucleophilic acyl substitution and acid catalyzed
nucleophilic acyl substitution for appropriate
reactions.
85
carbanions:
21.11(mechanisms), 21.18,p 817: 1,2,3,6, mechanism
for 6(a,d),25.1(a),25.8,25.10(a,b,c),25.16,
25.19(a-d),25.20(a-d),27.1,p.985: 2,3,7.
amines:
p.843: 1,2,22.5,22.6,3.
p.878: 1,2,4,5,9,7,11,12,29,30,32.
phenols:
p.913: 1,4,5,8,33.
aryl halides:
p. 968: 1,2,3,8.
Outline mechanisms for nucleophilic aromatic substitution (bimolecular) and the benzyne mechanism.
molecular
orbitals:
handout, 28.3,28.6,28.7,28.10.
heterocycles:
know the names of common heterocycles.
p 1074: 1,2.
polynuclear
aromatics:
1. Reactions. Predict the structures and names of the products
(if any) of naphthalene with:
a)
b)
c)
d)
e)
CrO3, acetic acid
O2,V2O5
Na,C2H5OH,reflux
Na,C5H11OH,reflux
f)
H2,Ni,heat,pressure
HNO3,H2SO4
g)
Br2
h)
conc. H2SO4, 80
i)
conc. H2SO4, 160o
acetyl chloride,AlCl3,CS2
j)
k)
l)
o
acetyl chloride,AlCl3,C6H5NO2
succinic anhydride,AlCl3,C6H5NO2
86
2. Reactions. Predict the structures and names of the products
of the reaction of:
anthracene with:
a) K2CrO7,H2SO4
b) Na,C2H5OH,reflux
c) Br2
phenanthrene with:
a) K2CrO7,H2SO4
b) Na,C5H11OH,reflux
c) Br2
d) Br2,FeBr3
3.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
4.
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
Predict the products of nitration of the following compounds:
1-methylnaphthalene
2-methylnaphthalene
1-nitronaphthalene
2-nitronaphthalene
1-naphthalenesulfonic acid
2-naphthalenesulfonic acid
N-(1-naphthyl)acetamide
N-(2-naphthyl)acetamide
alpha-naphthol
beta-naphthol
Outline syntheses of the following from naphthalene:
alpha-naphthol
beta-naphthol
alpha-naphthylamine
beta-naphthylamine
1-iodonaphthalene
2-iodonaphthalene
1-nitronaphthalene
2-nitronaphthalene
alpha-naphthoic acid
beta-naphthoic acid
4-(1-naphthyl)butanoic acid
alpha-naphthaldehyde
beta-naphthaldehyde
1-phenylazo-2-naphthol
87
o)
p)
q)
r)
s)
t)
u)
v)
w)
x)
y)
4-amino-1-naphthol
1-bromo-2-methoxynaphthalene
1,5-diaminoanaphthalene
4,8-dibromo-1,5-diiodonaphthalene
5-nitro-2-naphthalenesulfonic acid
1,2-diaminonaphthalene
1,3-diaminonaphthalene
ortho-aminobenzoic acid
phenanthrene
anthracene
9,10-anthroquinone
5. Haworth syntheses of the following starting with compounds
with fewer rings:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
k)
l)
m)
n)
2-methylnaphthalene
1-methylnaphthalene
1,4-dimethylnaphthalene
1,7-dimethylnaphthalene
1,6-dimethylnaphthalene
1,4,6-trimethylnaphthalene
1-phenylnaphthalene
anthracene
phenanthrene
9-methylanthracene
2-methylanthracene
9-methylphenanthrene
4-methylphenanthrene
1-methylphenanthrene
carbohydrates: define the following terms and give examples:
carbohydrate
monosaccharide, disaccharide,polysaccharide
aldose, ketose
pentose
reducing sugar
Tollen's reagent
Fehling's reagent
Benedict's solution
epimers
Ruff degradation
Kiliani-Fischer synthesis
D, L
glucoside
alpha-glucoside
beta-glucoside
anomers
113
CHE-313
TENTATIVE SCHEDULE
section
313-01
313-02
1.
2.
3.
1/27
1/29
2/3
1/28
1/30
2/4
4.
2/5
2/6
5.
6.
2/10
2/12
2/17
2/19
2/24
2/26
3/3
3/5
3/10
3/12
3/17
3/19
3/24
3/26
3/31,4/1
4/7
4/9
4/14
4/16
4/21
4/23
4/28
4/30
5/5
5/7
5/12
5/14
2/11
2/13
2/18
2/20
2/25
2/27
3/4
3/6
3/11
3/13
3/18
3/20
3/25
3/27
4/2,4/3
4/8
4/10
4/15
4/17
4/22
4/24
4/29
5/1
5/6
5/8
5/13
5/15
7.
8.
9.
10.
11.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
topic
check in
oxidation/IR & nmr
cont.
cont.
ID of unknown ketone
cont.
no lab
Reduct. of acetophenone
cont.
Grignard synthesis
of toluic acids
Esterification
cont.
Aldol condensation
cont.
Diels Alder
cont.
α,β-unsaturated ketone
no lab
cont.
Lidocaine
cont.
cont.
Qualitative analysis
Spring '03
reference
supplement
p. 842-845
Appendix 3
p. 855-858
Appendix 4
supplement
p. 888-889
supplement
supplement
supplement
p. 96-99
p. 409-411
supplement
p. 413-417
supplement
p. 485-533
114
CHEM-313
Instructor:
Office:
Phone:
Office Hours:
SYLABUS
Dr. J. L. Lyle
NSM D-323
(310)243-3388;243-3376
Will be announced in class; open door policy
Required Texts:
Introduction to Organic Laboratory Techniques Pavia, Kriz, Lampman
& Engel.
CRC Handbook of Chemistry and Physics (highly recommended)
Lab notebook
Safety goggles
1. Grading:
Traditional letter grades will be assigned on the
same basis as in CHE-312.
Lab reports
75%
Notebook
10%
Evaluation
15%
2. Lab reports and prelabs. A prelab is to be turned in 24 hours
before the scheduled lab (see futher below for format). A typed
lab report will be required for each experiment. The report is
due one week after the scheduled completion of the lab. These
reports are due at the scheduled start time for the lab. Late
reports will be penalized one letter grade for the first 24 hours.
Lab reports that are submitted more than 24 hours late will not be
accepted!
Please note that lab reports are not written in the lab notebook,
but are separate requirements. You will be given explicit
instructions about what each lab report is to contain. Lab reports
are to be your own work and not plagiarised from some other
student or lab report. Academic dishonesty will not be tolerated!
3. Notebook. A written record of what you are doing in the lab
will be kept in your notebook. You are expected to have your
notebook with you in the lab. Failure to do so can affect your
grade. The notebook entries will be written in ink. The carbon
copies that you make will be submitted with your lab reports.
4. Evaluation. Part of your grade will be an evaluation of your
lab technique, preparedness, punctuality, etc. by the instructor.
5. Safety. You must wear approved eye protection at all times in
the lab. Failure to do so will result in expulsion from the lab.
115
6. Prerequisite. You must have completed CHE-310 and CHE-311.
Corequisite is enrolment in CHE-310.
8. Attendance. You are expected to attend all laboratory
sessions. Make ups will only be allowed if arrangements are made
prior to the missed lab and for good reason.
9. Course goals, objectives, and requirements are covered
elsewhere in this syllabus.
Pre-labs:
For each preparative lab you are required to submit at least
24 hours before the lab a pre-lab writeup. The pre-lab is to be
written in your lab notebook and the carbon copies submitted for
review. These carbon copies will later be attached to your lab
report.
1. Title (be specific, eg. "Reduction of Acetophenone with
Sodium Borohydride"), name & date.
2. Balanced chemical equation(s) for the reaction(s) that
you are going to carry out.
3. Table of Physical Properties summarizing the physical
properties of the reactants, solvents, and products. Make
photocopies of the sample provided, or make up your own.
4. A step-by-step procedure for the reaction, separation,
and purification. Be specific as to amounts (moles & weight or
volume).
5. For multistep syntheses prepare a separate Table of
Physical Properties for each reaction in the sequence.
You may turn in pre-labs directly to the instructor or they
may be placed in his mailbox in the Chemistry Office (NSM B-302).
If you have not submitted a pre-lab before the lab you will not
be allowed to begin the experiment until the pre-lab has been
completed and okayed. Failure to submit pre-labs on time can
severely affect your grade.
116
Lab Reports
A typed lab report is required for each experiment. Reports
are due one week after the scheduled completion of the experiment
at 1:00 pm for section 01 and 9:00 am for section 02. Labs turned
in after these times will be penalized 10% per day late.
Follow the following format for preparative reports:
1.
Title, name & date (unknown #)
2.
Balanced equation(s) for the reaction(s) you carried out.
3.
Step-wise mechanism(s) for the reaction(s).
4. Physical data for your product(s) (weight, mp or bp,
%yield, & literature mp or bp for comparison).
5. Tabulation of spectral data. (Tables summarizing the IR
and nmr spectra and your interpretation). see attached.
6. Conclusions, comments, deviations, etc. Discuss your
results.
7.
Answers to the questions at the end of each preparation.
8.
Attach to the end of the report:
a) the pre-lab including table of physical properties
b) any additional carbon copies from your lab notebook
c) IR & nmr spectra, gc's, etc.
Products
With your lab reports you are to turn in the products that
you have synthesized in the laboratory. Note, the labels must
contain your name, the date, the identity of the contents, the net
weight, and the mp or bp. Solid products should be in wide-mouth
bottles and liquids in narrow-mouth containers.
117
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
Product(s)
fw
Moles
weight
(g)
volume
(mL)
density
(g/mL)
bp
mp
solubility
118
TABLE OF PHYSICAL PROPERTIES (This table must be completed before coming to lab!)
Reactants and
solvents
Product(s)
fw
Moles
weight
(g)
volume
(mL)
density
(g/mL)
bp
mp
solubility
119
CHE-313
Reporting IR and nmr spectra
Report the results of infrared and nmr spectroscopy in tabular
form. See example below:
For the nmr:
1. Draw the structure of the compound and label the groups
of hydrogens that give rise to each signal using a, b, c ... (let
a = most upfield).
2. Make a table showing the chemical shift, integration and
splitting pattern for each group of hydrogens assigned to the
structure.
example:
ethoxybenzene
a
1.3 ppm
3H
Ph-O-CH2CH3
c
b a
triplet
b
3.9 ppm
2H
quartet
c
6.6-7.2 ppm
5H
complex
For the IR:
Make a table listing in decreasing order all of the
absorbances and identify those that are important.
example: ethoxybenzene
frequency (cm-)
interpretation
3040
3000
2940
1600
1580
1500
1480
1390
1300
1240
1170
1120
1050
880
800
750
690
C-H stretch unsaturation, Ar-H
C-H stretch saturation
C=C stretch, aromatic ring
C=C stretch, aromatic ring
C-H bend, saturated
"
"
"
C-O stretch, ether
C-H out of plane bend mono-substitution
120
Oxidation of a side chain & introduction to IR and nmr
You will oxidize an unknown arene with KmnO4 to a benzoic
acid. See the procedure in this supplement. Because the starting
material is an unknown, the table of physical properties is a
little different from the ones you have previously prepared. You
will be given (on the unknown bottle) the molecular formula of
your unknown. Calculate the gram formula weight and the number of
moles contained in 1.0 grams. The amount of KMnO4 you will use is
based on the formula of your unknown.
You will identify the unknown arene from the melting point of
the acid product and the IR and nmr spectra of the unknown. Be
sure to balance your chemical equations correctly. No mechanism
is required for this report. Include the answers to the following
questions in your report.
Answer the following questions:
1. Write a balanced chemical equation for the permanganate
oxidation of p-xylene under basic conditions. See your general
chem text for review of balancing oxidation-reduction equations.
2. Write a balanced chemical equation for the permanganate
oxidation of tolune.
3. Write chemical equations to show how you would oxidize
toluene to benzaldehyde rather than benzoic acid. see M&B
4. Why is benzoic acid more soluble in base than in aced?
What is this difference in solubility used for?
5. Tert-butylbenzene is not oxidized by permanganate to
benzoic acid. Why not?
6. a) Draw all of the arenes with formula C7H7Br and show the
products of oxidation for each one. b) Look up the mp of each
product. c) Can you identify every isomer based on the melting
point of the carboxylic acid derivative? Explain.
7. Write a balanced equation for the reaction of potassium
permanganate with sodium bisulfite.
121
Identification of an unknown arene by oxidation to the carboxylic
acid; introduction to IR and nmr spectroscopy.
A classical approach to the identification of some aromatic
compounds is the oxidation of side chains to carboxylic acid
groups. Measurement of the derivative's melting point and
comparison with the known melting points of different benzoic
acids provided a means of identifying or eliminating certain
possible structures. For example: if a compound was found to
have the formula C8H10, it could be four different compounds:
ethyl benzene, o-xylene, m-xylene, or p-xylene. If you look up
the boiling points of these four compounds, they are very close to
each other. On the other hand, the melting points of the
corresponding carboxylic acids produced from the oxidation of the
side chains are distinctly different. When combined with
additional information, such as the IR and nmr spectra, the
melting point of the derivative will usually be sufficient to
determine the structure of the unknown.
You will be given a small sample of an unknown arene for
which the only information provided is the molecular formula. You
are to carry out the permanganate oxidation in alkalai solution
and isolate the carboxylic acid. You will measure the melting
point of the acid and compare it to the melting points of the
possible derivatives from your molecular formula. In addition,
you will obtain the IR spectrum of your original uknown and the
nmr spectrum.
procedure:
1. The apparatus consists of a 250 mL round-bottom flask fitted
with a reflux condenser.
2. Place about 1 gram (40 drops) of the unknown into the flask.
3. Add approx. 80 mL of water and 1-2 mL of 6M NaOH to the flask.
4. Using the powder funnel, introduce the required amount of
potassium permanganate (see table below) into the flask and add a
couple of boiling chips.
compound formula
C7H8
C8H10
C9H12
g
4
6
8
KMnO4/g unknown
g
g
g
5. Attach the reflux condenser and begin heating the mixture with
a heating mantle. Be careful when the mixture first starts to
boil as it has a tendency to "bump".
122
6. Continue the reflux for 2-3 hours. At the end of the first
period, cool the flask, label it, cork it, and place it in one of
the hoods until next lab.
7. Suction filter the contents of the round-bottom flask to
remove the solid MnO2.
8. Transfer the filtrate to a 250 mL beaker. Place the beaker in
a ice bath, and after the solution has cooled for 10 minutes,
acidify with 10 mL of 6 M H2SO4, while stirring. (If the solution
is still purple due to excess permanganate, destroy it by adding
no more than about 2 mL of 20% sodium bisulfite.
9. Test the solution with litmus to verify that it is acidic; if
not add more sulfuric acid.
10. Filter the precipitated acid with suction through a small
buchner funnel and wash with a few mL of cold water. (If no acid
has precipitated, consult with the instructor).
11. Recrystallize the acid from a suitable solvent (try water
first).
12. Let the product air dry, weigh it, package it, and obtain its
melting point.
123
Identification of an unknown carbonyl
In this experiment you will be given an unknown aldehyde or
ketone. You will obtain the IR and nmr spectra, do the Tollen's
test, and prepare two solid derivatives. In the report, identify
the unknown and compare the experimental values with the ones
given in the text; make a TABLE for comparison. Be sure to
include balanced equations for the Tollen's test, the preparations
of the derivatives, as well as appropriate mechanisms. Do not
weigh derivatives or calculate % yield.
Prepare the 2,4-dinitrophenylhydrazone derivative of your unknown.
The reagent is already prepared. Mix 10 drops (0.5 mL) of your
unknown in 20 mL of 95% ethanol. To this solution, add 15 mL of
the 2,4-DNPH reagent. Shake the mixture vigorously. If a
precipitate does not form immediately, let it stand for 15
minutes. Suction filter the solid derivative and recrystallize
from 95% ethanol. After air drying, obtain the mp.
Make an additional derivative, the semicarbazone, according to the
directions on page 888 and obtain the mp.
Test the unknown with Tollen's Reagent (p 511) to see if it is a
ketone or an aldehyde. Page 878-879 lists possible aldehydes in
increasing order of boiling point and the melting points of easily
prepared derivatives. Ketones are listed in the table on pages
879-880.
Do a simple distillation to measure the boiling point of your
unknown carbonyl compound.
Obtain the IR and nmr spectra of your unknown carbonyl compound.
Answer the following questions:
1) An unknown organic compound (b. 212-216 oC) gives a
positive 2,4-DNPH test and is positive with Tollen's reagent. A
semicarbazone derivative is made that melts at 228-232 oC. What is
the identity of the unknown? What would you do next?
2) Predict the products of the reaction of the following
with silver nitrate in ammonium hydroxide:
cylcohexanone
formaldehyde
acetone
acetophenone
butyraldehyde
124
3) In the reaction of an aldehyde or ketone with derivatives
of ammonia, the reaction can be catalyzed by sulfuric acid.
However, it is important that the pH not be too low since the
reaction will slow down at very high acid concentrations.
Explain.
4) Ketones do not oxidize readily. However, cyclohexanone
will react with powerful oxidizing agents at high heat to adipic
acid (HO2C-(CH2)4-CO2H). The reaction is not really one of the
ketone, but the enol. Write equations to show how this is
possible.
125
Reduction of acetophenone to 1-phenylethanol
-
1.2 g NaBH4
+
25 mL EtOH (95%)
- dropwise (controlled addition; keep temperature < 50o ) of 12 mL
of acetophenone
-
let stand 15 minutes
- acidify with 10 mL (3M) HCl
- boil down on hot plate until you have two layers
- extract with (1) 20 mL Et2O
(2) 10 mL Et2O
-dry combined ether extracts over anh. MgSO4 TWICE!
-distill off Et2O
(  waste bottle )
-residue = crude product (bp 102.5 – 103.5 @ 19 Torr), do not
distill
IR, nmr of product AND acetophenone
We will not purify the product with vacuum distillation. After
the removal of the diethyl ether, package, weigh and label the
crude product. Obtain IR and nmr on both the acetophenone and the
product.
Answer the following questions:
1. What was the molar ratio of NaBH4 to acetophenone that you used
in the experiment. What is the theoretical ratio? Why did you
use more than the theoretical ratio?
2. After the reaction of the carbonyl with sodium borohydride,
the mixture is treated with water and acid to produce the desired
alcohol. Indicate the source of the alcoholic hydrogen in the
product.
3. Although sodium borohydride reacts slowly with methanol, when
mineral acid was added, it rapidly decomposed with the evolution
of hydrogen. Explain.
4. Why is 1-phenylethanol more prone to dehydration than 2phenylethanol?
126
5. What is the structure of the white precipitate that forms in
the reaction of acetophenone with NaBH4?
6. Write an equation for the reaction of the white ppt with water
and HCl.
7. Draw the structure of the products of the reduction of each of
the following with NaBH4:
a)
b)
c)
d)
cyclohexanone
3-cyclohexen-1-one
1,4-butanedial
4-oxohexanal
8. Draw the structure of the products for the reduction of each
of the compounds in question 7 with excess hydrogen gas over
Nickel.
9. Why does the concentration of the ethanolic reaction mixture,
followed by the addition of HCl, result in the formation of two
layers?
127
Organometallics
You will be running a Grignard synthesis of a carboxylic acid
from the reaction of a Grignard Reagent and carbon dioxide. See
your lab text: p. 280-283 & p. 285-288. You will modify the
procedure to make either p-tolyl or o-tolyl magnesium bromide from
p-bromotoluene (section 01) or o-bromotoluene (section 02) and
react it with carbon dioxide in the form of dry ice. Modify the
procedure in your text for the synthesis of phenyl magnesium
bromide as follows:
Take one-fifth of the required amounts of the bromotoluene
and diethyl ether and place the mixture in a dry test tube. Add
some of the magnesium metal. Scratch and break up the metal with
a stirring rod to begin the reaction. Once the reaction has
started, add the mixture to the ether and remaining magnesium in
the round bottom flask with 10 mL of diethyl ether. Begin the
slow addition of the bromotoluene/ether mixture as detailed in the
lab text.
Answer the following questions:
1) Where in the nmr spectrum would you see the carboxylic
acid hydrogen?
2) Why must all equipment be dry when reacting tolyl
magnesium bromide with carbon dioxide? (show equations)
3)
a) Explain the difference between "inverse" and
"normal" addition of organometallics and substrates.
b) Which was done in this experiment? Why?
4) Write chemical equations to show all of the different
methods that can be used to synthesize tertiary alcohols with
Grignard reagents.
4) Write all steps in the mechanism for the reaction of an
ester with a Grignard reagent.
5) What side reactions are possible during the formation of
a Grignard reagent? Write structures. How were these separated
from the product?
6) p-Toluic acid cannot be made from p-xylene by oxidation.
Explain.
Answer questions 1, 2, 5 on page 288.
128
Esterification
You will make isopentyl acetate (banana oil) according to the
instructions in your lab text on page 96. Obtain the IR and nmr
spectra of the product.
Answer the following questions as part of your report:
1)
a) If the Keq for the esterification of acetic acid
with isopentyl alcohol is 3.0, what is the maximum amount of
isopentyl acetate that can be recovered at equilibrium if a 1:1
mole ratio of acid:alcohol is used?
b) If a 1:5 mole ratio is used?
c) 5:1 mole ratio?
2) What role does sulfuric acid play in this reaction?
Explain; show equations.
3) Tell what effect doubling the concentration of sulfuric
acid would have on the yield of the ester.
4) Why were the contents of the round bottom flask after
reflux poured into 10 mL of water?
5)
6)
ester?
Why do we wash the ester with sodium carbonate solution?
Why would solid NaOH not be a good drying agent for the
7) How would you distinguish between the nmr spectra of
methyl benzoate and phenyl acetate?
129
Aldol condensation
You are to prepare anisalacetophenone (AKA 4-methoxychalcone)
via an aldol condensation according to the directions on page 411
of your lab text. You will recrystallize the crude product from
95% ethanol. Run the nmr and IR (CCl4) spectra of your product.
answer the following questions:
1)
In the aldol condensation you ran:
a) Why doesn't the ketone undergo a self-condensation?
b) Why doesn't the aldehyde undergo the Cannizzaro
reaction?
c) Write equations for both of the above reactions.
2) Are there geometric isomers of the product of this
synthesis? Draw them. Is the reaction stereoselective or
stereospecific? Which product is actually formed and why.
3)
Predict the products of the following:
a)
b)
c)
d)
e)
butyraldehyde, dil. NaOH
formaldehyde, conc. NaOH
acetone, p-tolualdehyde(2 mol), dil NaOH
2,2-dimethylpropanal, formaldehyde, conc. NaOH
benzaldehyde, methyl acetate, sodium methoxide
4) Why does the intermediate in the synthesis undergo
spontaneous dehydration?
5) Show the stereochemistry of the hydroxylation with
potassium permanganate of trans- anisalacetophenone using Fischer
projections.
Answer question 4 on page 412 of your lab text.
130
Diels Alder
Read pages 427-433.
Run the Diels Alder condensation reaction between alphaphellandrene and maleic anhydride according to the directions
below. Obtain IR (KBr pellet) spectrum of the product.
Write up a pre-lab for the condensation of α-phellandrene (2methyl-5-isopropyl-1,3-cyclohexadiene) and maleic anhydride.
You won't find the product in the CRC.
The α-phellandrene that we have is not pure, it only contains
70% α-phellandrene by weight. You will need to figure how much of
the impure compound to weigh out that will contain 0.050 mole of
the α-phellandrene.
In a 100-mL round-bottom flask put 0.050 mole of maleic
anhydride and the weight of impure α-phellandrene that contains
0.050 mole. Add 25 mL of ethyl acetate, attach a reflux
condenser, and heat on a hot water wath for one hour. Cool in an
ice-water bath and then suction filter. Recrystallize the product
from ethyl acetate, vacuum filter, let air dry, weigh, package,
and obtain the IR spectrum (KBr method).
answer the following questions:
1) Why is the endo product usually preferred in Diels-Alder
condensations?
2) In your product, which way is the isopropyl group pointed?
Explain.
3) The product of your synthesis has three chiral centers. Draw
the product and label each chiral center with and asterisk (*).
How many stereosiomers are theoretically possible? Only one
stereoisomer is actually formed in this reaction, explain.
4)
Predict the products of the following:
a)
b)
c)
d)
e)
1,3-butadiene + 2-butyne
1,3-cyclopentadiene + cis-2-butene
1,3-butadiene + dimethyl maleate(methyl ester of maleic acid)
(2 mol)1,3-cyclopentadiene + p-benzoquinone
dicylopentadiene + heat (retro Diels-Alder)
5) Explain why the diene must be in the sigma-cis conformation in
order to undergo a Diels-Alder reaction.
131
Preparation of an α,β-unsaturated ketone via Michael Addition
combined with an aldol condensation.
The procedure for this experiment is in your text:
You will obtain the IR spectrum of the product.
Answer questions 1-4 on page 416.
p. 413-416.
132
Lidocaine
You will synthesize lidocaine via a series of synthetic
reactions according to the instructions below. A single report is
required with IR and nmr spectra of the final product. Be sure to
calculate % yield for each step of your synthesis as well as the
overall % yield.
multistep synthesis of lidocaine
first lab:
Reduction of 1,3-dimethyl-2-nitrobenzene to 2,6-dimethylaniline
Ar-NO2
+
SnCl2.2H2O, HCl
--->
Ar-NH3+,Cl-
+
SnCl4
-make up the following two solutions:
solution 1: 0.10 mole (22.6 g) SnCl2.2H2O in 40 mL of conc.
HCl (warm to dissolve)
solution 2: 0.033 mole (5 g, 4.5 mL) 1,3-dimethyl-2nitrobenzene in 50 mL acetic acid
-mix the two solutions and let stand for 15 minutes
-after fifteen minutes, cool in ice bath and vacuum filter
Ar-NH3+,Cl-
+
KOH
--->
Ar-NH2
-tranfer solid to a flask and add 25 mL of water, make strongly
basic with 40-50 mL of 8M KOH (caution!)
-cool to room temperature with ice bath
-extract with (1) 25 mL diethyl ether
(2) 10 mL diethyl ether
-wash combined ether extracts with 10 mL water; repeat
-dry over anh. K2CO3
-filter into pre-weighed RB flask and remove diethyl ether by
distillation (ether --> waste bottle)
-reweigh flask
133
α-chloro-2,6-dimethylacetanilide
Ar-NH2
+
Cl-CH2COCl
-residue from above
+
--->
Ar-NHCOCH2-Cl
25 mL acetic acid
-add (3.7 g, 2.6 mL) α-chloroacetyl chloride (caution!)
-warm to 40-50oC
-add solution: (5 g NaO2CCH3.3H2O in 100 mL water)
-cool, vacuum filter, air dry, weigh, mp
second lab:
lidocaine
Ar-NHCOCH2-Cl + NH(CH2CH3)2 
Ar-NHCOCH2-N(CH2CH3)2
-note: all reagents and apparatus must be dry!
-in a 250 mL RB flask, combine the α-chloro-2,6dimethylacetanilide from above with 45 mL toluene
-calculate the number of moles of α-chloro-2,6-dimethylacetanilide
and add three times that number of moles of diethylamine to the
RB.
-attach a water cooled condenser and reflux for 90 minutes.
-cool in an water bath and vacuum filter off the solid that forms.
(this is not your product!)
-transfer the filtrate to a separatory funnel and extract with two
25 mL portions of 3M HCl.
-combine the aqueous layers in a 250 mL Erlenmeyer flask and add
50 mL of 8 M KOH to make the solution stronly basic.
-warm the mixture and blow across the surface to remove any excess
diethylamine
-cool in an ice bath, continuing to blow and scratch until
crystals form.
134
-vacuum filter the crude lidocain, wash the crystals with cold
water and remove from the filter paper immediately.
-let dry on a watch glass, package, weigh, mp, IR & nmr spectra.
Answer the following questions:
1) Write a balanced chemical equation for the reduction of
nitrobenzene with Fe in HCl to form aniline. (Fe --> FeCl3)
2) Draw the structures of at least two by-products produced in
the reaction in 1).
3) Why does 2,6-dimethylaniline react with chloroacetyl chloride
to produce an amide rather than a secondary amine?
4) Lidocaine is commercially sold in the form of the hydrogen
chloride salt. Why?
5) In the reduction of 2,6-dimethylnitrobenzene with stannous
chloride, what is the structure of the ppt that is collected by
suction filtration?
6) What is the precipitate collected by filtration after the
reaction with diethylamine?
7) Why do we use three moles of diethylamine for every mole of
the anilide?
135
Qualitative analysis
You will receive three unknown organic compounds which you
are to identify by a traditional qualitative analysis scheme. The
report will consist of a form that you will fill out. Read p 485490 in your text.
Qualitative Organic Analysis
The analysis experiment is equivalent to identifying a substance
about which you have absolutely no information: the contents of
an unlabeled bottle; a natural product isolated from the leaf of a
tropical plant; a component of a competitor's formulated product;
etc. Such an analysis requires a systematic approach, as is
described in in your text.
1.
Prior to receiving your unknown sample, a practice sodium
fusion (analysis for constituent elements) must be done.
Read:
page 500-502
A solid "known" mixture of organic compounds that contains
nitrogen, sulfur, and halogen (N, S, X) is to be used. After
you have observed the demonstration of the sodium fusion
technique, you are to perform the sodium fusion with the
"known" mixture, and then test the resulting aqueous solution
for the constituent ions.
NOTE: Do not carry out the procedures to determine the
identity of the halogen (or halogens) in the known or in your
unknown. If you do get a positive test for halogen with Ag+,
you will be able to determine if the X is F, Cl, Br, or I (or
a combination) from subsequent tests and/or clever reasoning.
2.
When you have completed the practice sodium fusion and ion
tests, obtain a numbered vial containing your unknown from
the instructor. Record the unknown number in your notebook
immediately!
3.
Perform the analysis according to the list on page 485,
including the indicator tests according to the attached
handout.
4.
If you wish to carry out any classification or functional
group tests with known compounds, ask the instructor who will
cheerfully fulfill your request.
136
5.
Consult the Handbook of Tables for Organic Compound
Identification and the tables in your text (p. 878-888).
Qualitative Analysis -- preliminary classification
Solubility tests:
To carry out the solubility tests,
approximately 0.1 g or 0.1 mL of the substance is added to 3 mL of
the solvent. If most of the material appears to dissolve, the
compound is considered soluble. If there is no immediate change,
especially with a solid unknown, the mixture should be thoroughly
stirred with a glass rod and at least 2 minutes allowed to elapse
before a decision is made.
The solubility tests must be applied in the sequence given
below to avoid misleading observations.
a. Solubility in water. A compound that is soluble in water must
be at least somewhat polar.
b. Solubility in ether. A compound that dissolves in water is
tested for solubility in diethyl ether. Organic compounds that
contain more than one polar functional group are not likely to
dissolve in ether. Only compounds that have one polar group and a
relatively small number of carbon atoms are expected to dissolve
in both polar and nonpolar solvents.
c. Solubility in aqueous acid or base. A water-insoluble organic
acid should dissolve in an aqueous base; an organic base that is
not soluble in water should dissolve in aqueous acid. The
observed solubility in each case is the result of the formation of
an ionic salt which remains dissolved in the aqueous medium. It
should be obvious that these tests are applied only if the
original compound does not dissolve in water. If the substance is
found to be soluble in 5% NaOH, indicating that it is an acid, it
is tested further with 5% sodium hydrogen carbonate. Only acids
stronger than carbonic acid will dissolve. A compound may
therefore be classified as a strong or weak acid on the basis of
these two solubility tests. An organic base can be identified by
its solubility in 5% hydrochloric acid. No further classification
is possible. If a compound is found to be an acid, it should also
be tested with hydrochloric acid on the chance that it may contain
both acidic and basic functional groups (e.g., an amino acid).
d. Solubility in sulfuric acid. A compound that is insoluble in
water, hydrochloric acid, and sodium hydroxide is considered to be
neutral. Those substances that contain nitrogen or sulfur are not
tested further and are classed as nitrogen-sulfur neutrals (class
M). Other compounds are tested for solubility in concentrated
137
sulfuric acid. In this test, a solution in the sense of an
ordinary aqueous solution is not necessarily formed. If heat is
evolved, a color develops, or any other change indicative of a
reaction is seen, it is concluded that the substance is "soluble"
in H2SO4.
Solubility classification of some organic compounds:
S1 :
soluble in water and soluble in diethyl ether
oxygen and nitrogen compounds having less than five carbon
atoms: monofunctional alcohols, aldehydes, amines, carboxylic
acids, ketones.
S2 :
soluble in water and insoluble in diethyl ether
polyfunctional oxygen and nitrogen compounds: diols, triols,
etc.; polyamines; dicarboxylic acids.
A1 (weak acids) :
soluble in dilute sodium hydroxide
phenols, beta-diketones.
A
2
(strong acids) :
soluble in dilute sodium bicarbonate
carboxylic acids, polynitrophenols, polyhalophenols, acyl
halides.
B (bases) : soluble in dilute hydrochloric acid
amines (except diaryl and triarylamines)
N1 (neutrals) :
soluble in conc. sulfuric acid
alkenes, some arenes, ethers, water-insoluble: alcohols,
aldehydes, esters, ketones.
N2 (neutrals) :
insoluble in conc. sulfuric acid
alkanes, halides, diarylethers.
M (nitrogen-containing neutrals)
amides, nitrocompounds, diaryl- and triarylamines,
nitroarylamines.
138
Indicator Classification Method:
The solubility method suffers from several shortcomings. One
is that it is difficult to estimate solubility in borderline
cases. There are also some instances in which a solid substance
dissolves, only to react with the solvent to form an insoluble
product. The indicator method overcomes these difficulties and
also provides a more specific classification. That is, it is
possible to classify an acid as weak, intermediate, or strong,
rather than just weak or strong as in the solubility system.
Bases can also be classified as weak, intermediate, or strong.
A set of four indicators, A-I, A-II, B-I, and B-II is
required. To carry out the test, 1 mL of the indicator is placed
in a small test tube and one drop of a liquid or about 30 mg or a
solid (about as much as can be carried on the tip of a small
spatula) is added to the indicator. The effect on each indicator
solution is described below:
A-I Indicator (original color: purple)
If the color changes from purple to yellow, the compound is
an intermediate acid (Ai) or a strong acid (As). If the color
change is from purple to green, the unknown is a weak acid (Aw).
To distinguish between Ai and As, you must use the A-II indicator.
A-II Indicator (original color: blue-violet)
A change from blue-violet to yellow occurs if the unknown is
an intermediate acid. A strong acid causes a change from blueviolet to a shade of red.
B-I Indicator (original color: Purple)
Any base changes the color from purple to yellow.
B-II Indicator (original color: Yellow)
A weak base (Bw) has no effect (color remains yellow), while
an intermediate base (Bi) produces a change from yellow to blueviolet. (There are relatively few strong organic bases. Although
it is possible to detect strong organic bases by special treatment
of the indicators, they will not be considered here.
139
Caution: The indicators are made up in nonaqueous solvents. The
addition of water to any of the indicators may cause a color
change. It is imperative therefore that a clean, dry test tube be
used for each test, and the sample tested must be free of water.
Indicator Classification of Some Organic Compounds:
Strong acids (As):
nitrophenols.
acyl halides, some carboxylic aicds,
Intermediate acids (A ): carboxylic acids, o- and pi
hydroxyaromatic aldehydes and ketones, polyhalophenols.
Weak acids (Aw):
phenols, beta-diketones, some aryl esters.
Intermediate bases (Bi):
aliphatic amines, heterocyclic amines.
Weak bases (Bw): primary arylamines, arylalkylamines,
heterocyclic amines.
Neutrals (do not contain nitrogen): hydrocarbons, halides,
alcohols, aldehydes, ketones, esters, ethers.
Neutrals (contain nitrogen): diarylamines, triarylamines,
nitriles, nitrocompounds, amides, polynitroarylamines,
polyhaloarylamines.
140
Chemistry 313
QUALITATIVE ORGANIC ANALYSIS REPORT
Name
Date
Unkn. No.
1.
Identity of Compound
Physical properties of purified material:
physical state
color
b.p.
m.p.
refractive index (liq. only)
2.
3.
a)
other
Elemental Analysis: elements in addition to C, H, O
Preliminary Classification
Solubility tests (write "s" if soluble; "i" if insoluble).
H2O
Et2O
HCl
NaOH
NaHCO3
H2SO4
Classification
b)
Indicator tests (note the color change, if any)
A-I
A-II
B-I
B-II
Classification:
4.
Functional Group Tests
On a separate sheet of paper, prepare a table with the column headings:
Reagent, Result, and Inference. In the appropriate spaces, list the
actual reagent and observed result of every functional group test applied
to the unknown, and the inference drawn in each case. (See sample
below.)
Reagent
2,4-DNPH
Tollens
NH2OH, KOH
Result
Inference
orange ppt; red color with alc.KOH
carbonyl group
no silver mirror or ppt
ketone(no aldehyde)
no purple color
no ester group
5.
Probable Compounds: List all compounds with m.p. or b.p. within 5o of that of
the unknown, which could be identical to the unknown. Also list the useful
derivatives and their m.p.'s.
6.
Derivatives made: List the derivatives of the unknown that were actually
prepared and their observed m.p.'s.
Spectroscopic Data: Tabulate ir and nmr data, if obtained.
7.
141
Chemistry 313
QUALITATIVE ORGANIC ANALYSIS REPORT
Name
Date
Unkn. No.
1.
Identity of Compound
Physical properties of purified material:
physical state
color
b.p.
m.p.
refractive index (liq. only)
2.
3.
a)
other
Elemental Analysis: elements in addition to C, H, O
Preliminary Classification
Solubility tests (write "s" if soluble; "i" if insoluble).
H2O
Et2O
HCl
NaOH
NaHCO3
H2SO4
Classification
b)
Indicator tests (note the color change, if any)
A-I
A-II
B-I
B-II
Classification:
4.
Functional Group Tests
On a separate sheet of paper, prepare a table with the column headings:
Reagent, Result, and Inference. In the appropriate spaces, list the
actual reagent and observed result of every functional group test applied
to the unknown, and the inference drawn in each case. (See sample
below.)
Reagent
2,4-DNPH
Tollens
NH2OH, KOH
Result
Inference
orange ppt; red color with alc.KOH
carbonyl group
no silver mirror or ppt
ketone(no aldehyde)
no purple color
no ester group
5.
Probable Compounds: List all compounds with m.p. or b.p. within 5o of that of
the unknown, which could be identical to the unknown. Also list the useful
derivatives and their m.p.'s.
6.
Derivatives made: List the derivatives of the unknown that were actually
prepared and their observed m.p.'s.
7.
Spectroscopic Data:
Tabulate ir and nmr data, if obtained.
142
Chemistry 313
QUALITATIVE ORGANIC ANALYSIS REPORT
Name
Date
Unkn. No.
1.
Identity of Compound
Physical properties of purified material:
physical state
color
b.p.
m.p.
refractive index (liq. only)
2.
3.
a)
other
Elemental Analysis: elements in addition to C, H, O
Preliminary Classification
Solubility tests (write "s" if soluble; "i" if insoluble).
H2O
Et2O
HCl
NaOH
NaHCO3
H2SO4
Classification
b)
Indicator tests (note the color change, if any)
A-I
A-II
B-I
B-II
Classification:
4.
Functional Group Tests
On a separate sheet of paper, prepare a table with the column headings:
Reagent, Result, and Inference. In the appropriate spaces, list the
actual reagent and observed result of every functional group test applied
to the unknown, and the inference drawn in each case. (See sample
below.)
Reagent
Result
DNPH
orange ppt; red color with alc.KOH
Tollens
no silver mirror or ppt
NH2OH, KOH
no purple color
Inference
carbonyl group
ketone(no aldehyde)
no ester group
2,4-
5.
Probable Compounds: List all compounds with m.p. or b.p. within 5o of that of
the unknown, which could be identical to the unknown. Also list the useful
derivatives and their m.p.'s.
6.
Derivatives made: List the derivatives of the unknown that were actually
prepared and their observed m.p.'s.
7.
Spectroscopic Data:
Tabulate ir and nmr data, if obtained.