ORGANIC CHEMISTRY II
LABORATORY MANUAL
By
STEPHEN ANDERSON
And
ROBERT SHINE
RAMAPO COLLEGE OF NEW JERSEY
MAHWAH, NEW JERSEY
JANUARY 2009
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
ORGANIC CHEMISTRY II
LABORATORY MANUAL
DR. STEPHEN ANDERSON
DR. ROBERT SHINE
RAMAPO COLLEGE OF NEW JERSEY
CONTENTS AND SCHEDULE:
LAB 1
CHECK IN, SAFETY AND PROCEDURES
LAB 2
SODIUM BOROHYDRIDE REDUCTION
LAB 3
HYPOCHLORITE OXIDATION - GREEN CHEMISTRY
LAB 4
GRIGNARD REACTION
LAB 5
DIELS ALDER REACTION
LAB 6
NITRATION OF METHYL BENZOATE
LAB 7
FRIEDEL-CRAFTS ALKYLATION
LAB 8
QUALITATIVE ORGANIC ANALYSIS AND SIM-ORG
LAB 9
ALDOL CONDENSATION REACTIONS
LAB 10
WILLIAMSON SYTHESIS
LAB 11
ANALYSIS OF CARBOHYDRATES
LAB 12
HYDROLYSIS OF METHYL BENZOATE - GREEN METRICS
LAB 13
REVIEW - GREEN METRICS, SIM-ORG AND CHECKOUT
LABORATORY FINAL EXAMINATION
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
ORGANIC CHEMISTRY II
LABORATORY MANUAL
2
APPENDICES
APPENDIX LIST:
APPENDIX A:
QUALITATIVE ORGANIC ANALYSIS AND SIM-ORG
APPENDIX B:
SAFETY ISSUES
APPENDIX C:
COMMENTS ABOUT WRITING STYLE
APPENDIX D:
MEASUREMENTS AND SIGNIFICANT FIGURES
APPENDIX E:
PERCENT YIELD CALCULATION METHOD
APPENDIX F:
GREEN METRICS
APPENDIX G:
CHEMICAL DATA
ACKNOWLEDGEMENTS: The Authors wish to thank the following
people for their assistance with this manual: Carol Ichinco
(Laboratory Coordinator), Thomas Drwiega (Laboratory
Technician), Gurpreet Kaur (Honors Research Student), Benjamin
Barrios (Research Student), and all the other Instructors who
have taught Organic Chemistry Laboratory sections for the past
few years. Dr. Scott Frees and Jeffrey Ludwig are acknowledged
for their work in writing and developing the Sim-Org qualitative
organic analysis simulation program.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 1:
LABORATORY PROCEDURES
ORGANIC CHEMISTRY LABORATORY PROCEDURES
SCOPE OF THE COURSE:
3
This course offers a comprehensive introduction to
laboratory techniques in organic chemistry for science majors.
Chemistry is a mature science that continues to expand and
evolve in step with recent developments in science and
technology. Students will perform experiments that put into
practice the ideas discussed in lecture.
E-MAIL AND INTERNET USE:
Use will be made of e mail (Luminis) and the Internet to
provide important instructions to students concerning laboratory
material. Students are encouraged to contact the Instructor in
person or by e mail for additional help, if needed. Information
about the course may be transmitted periodically by the
Instructor via a web site for the course. Students should check
this web site at least once a week. Students may not submit lab
reports via e mail or e mail attachments or by fax. Lab reports
must be submitted as paper copy.
ATTENDANCE:
Each lab session will begin at the scheduled time.
Attendance at all laboratory sessions is mandatory and will be
recorded. If you are late, it will be noted and recorded. A
missed laboratory experiment cannot be made up at another time
and any missed laboratory session will result in a grade of zero
(0) for that experiment unless an alternate library report is
completed. During the course of the semester you will be
allowed to substitute one alternate report for any one lab
period you cannot attend. You must discuss the content and
deadline of the alternate report with the Instructor as soon as
possible after your absence.
SPECIAL NEEDS:
Students with special needs who are registered with the
Office of Specialized Services and require special
accommodations should notify the Instructor as soon as possible.
GRADING:
Each laboratory session will be graded by a procedure
explained to you by your laboratory instructor. Your in-lab work
and your report will be used to determine your grade.
The
final laboratory exam will account for about 20% to 30% of your
final laboratory course grade. In grading laboratory sessions,
the following will be considered: meeting deadlines, submitting
the necessary forms and reports on time and in good order, being
on time for lab, and working in a safe and efficient manner.
Your practical bench skills and laboratory results will also be
4
analyzed, along with your ability to effectively explain and
discuss them in your lab report.
SAFETY:
As with many activities in daily life, working in the
organic chemistry laboratory poses some hazards that you must
recognize. Many of the chemicals used can be toxic if not used
correctly. Also, many substances you will use are flammable and
must be kept away from sources of heat that could cause them to
ignite and start a fire. Glassware can be broken and cause
cutting hazards. You must always come to the laboratory
prepared so that you will be aware of the unique hazards you
will confront. You must consult the MSDS forms for the
chemicals you will use so that you will know their toxic and
flammability properties. You can find MSDS data on the internet
by typing the chemical name, a space followed by msds in a
Google search box (for example: acetone msds). If you have any
questions about the experiment you are performing or the
chemicals you are using, please ask the Instructor before you
begin work. When you are done with the experiment, the
chemicals you have should be discarded as hazardous waste or
reclaimed material and placed in the proper containers. If you
are pregnant or expect that you may become pregnant, you should
consult with a medical doctor about the potential hazards
involved with exposure to organic chemicals. See Appendix B for
more information about safety.
EYE PROTECTION:
Students are required to have department approved lab
goggles that must be worn at all times in the laboratory when
experimental work is being done. Students who fail to wear eye
protection could be asked to leave the lab by any employee of
the College. It is not recommended that you wear contact lens
in the laboratory.
PRE-LABORATORY PREPARATION:
It is imperative that students be prepared to perform the
scheduled experiments. An unprepared student is a hazard in a
chemistry laboratory. In order to prepare for the experiment,
students are expected to read the appropriate laboratory
experiment prior coming to the lab. Students may be tested at
the beginning of the lab period to ensure they are prepared to
begin work.
LABORATORY NOTEBOOK:
Students should have a notebook that will be used in the
lab for recording all experimental data. A title should appear
5
at the top of the page for each new experiment. Data obtained
during an experiment should always be neatly and clearly
recorded in this notebook. You should use the department
approved notebook for this course. You will be required to turn
in a copy of your experimental data sheet before you leave the
lab at the end of the period. You must include your name, the
name of the experiment, and the date of the lab period on the
data page you submit which will graded as part of your report
grade. Any measurement data must have the numerical value
recorded to the correct number of significant figures and the
units of that measurement, such as 1.234 g for a weight
measurement.
LAB REPORTS:
Before leaving the laboratory, each student must submit a
laboratory data sheet as described above. Lab reports can only
be submitted for labs that have been attended and must be
submitted at the beginning of the lab session following the lab
that is being reported. Points will be deducted for lateness or
for an incomplete lab report. No lab report for a given
experiment will be accepted after graded reports for that lab
have been returned to the class. Generally, graded lab reports
will be returned in the next class meeting after the report is
submitted. A score of zero is assigned for a report if the lab
report is not submitted.
FORMAT OF LAB REPORT:
Laboratory reports must be typed on 8.5 x 11 inch white
paper. The report should have a professional appearance and it
must demonstrate that much thought and care went into its
preparation. Some comments about report writing style appear in
Appendix C. Spelling and grammar count. All laboratory reports
must be written in the following format that conforms to the
guidelines set forth by the American Chemical Society:
COVER PAGE
Place the following information in the upper right
hand corner of the title page or first page of the report:
Title of the experiment, your name, date of submission
ABSTRACT
The abstract consists of two to five sentences that
concisely inform the reader of the nature of the experiment
that was performed and a brief summary of your final
results. Note that the abstract is read immediately after
the title and hence need not repeat any information that
already appears in the title. Though the abstract appears
at the beginning of the lab report, it should be the last
section of the report that is composed. The abstract
6
should be about 50 to 100 words and should give a concise
description of the experiment and the important results
that were obtained. It should not be too general or too
specific.
INTRODUCTION
The introduction consists of three to five paragraphs
that relate only the most essential elements of theory to
the reader. Consult other sources such as a chemistry
textbook for this information. Include only enough theory
so that the reader is made to understand the basic physical
and chemical principles involved in this experiment. If
applicable, any pertinent mathematical and chemical
equations must be given in this section. The introduction
should conclude with a one- or two-sentence paragraph that
explains the objective or goal of the experiment.
SAFETY
Students shall describe all relevant safety
precautions that were observed during the course of the
experiment. Information about the hazards that may be
encountered is particularly important. Material Safety
Data Sheet information should be included. You should give
a summary of the pertinent data (such as: toxicology,
flammability, and physical properties) and not just a copy
of the MSDS.
EXPERIMENTAL
For our purposes, the experimental section will
consist of a short paragraph that includes a sentence that
refers the reader to some source for the procedure. For
example, the student may write: "The procedure for this
experiment appears in the web page for the course (1)."
The number in brackets refers to the citation number. This
number is used to refer the reader to the citation in the
References section where the full reference (including
information such as the name of the author, title of book
or web site, date of publication, and page number or exact
web address) will appear next to number 1. In addition to
the reference citation, any deviations from the published
procedure and any experimental hints or tips that may aid
the reader in understanding and repeating the experiment
should be included. For example, ‘In this experiment, the
instructor requested that 0.05M HCl be used instead of
0.10M as specified in the module.’
RESULTS
This section consists of a written paragraph that
refers the reader to tables, graphs, data sheets, and
figures that contain your data. It is especially important
to inform your reader how your experimental data were used
7
to calculate your final results. You must explain how you
determined your final results. Include sample calculations
with an accompanying explanation. The use of a spreadsheet
program (such as Microsoft Excel) for calculations,
tabulation of results, and graphing is encouraged.
DISCUSSION
This section is used to indicate to the reader how the
results relate to the theory and whether or not the
objective was met. In addition, the final results must be
compared to literature values, if available. Reasonable
sources of error should be listed and discussed with
respect to their contribution to the final results. The
discussion provides a good indication of the student's
comprehension of the material. A good discussion should
show that the student was able to correctly interpret the
data and to relate the results to the scientific principles
being tested by the experiment. If the experiment was not
successful, then the discussion is equally important in
stating the reasons for the outcome. A good discussion can
be written regardless of the success of the experiment.
CONCLUSION
This section should include a summation of the Results
and Discussion sections. It should only be about 1
paragraph long and is intended to draw together all the
pertinent information that has been determined from the
experiment.
REFERENCES
This section consists of a numbered listing of
literature or internet references that were used to perform
the experiment and that were used to write the lab report.
This includes a full reference to the lab module and any
other publications or correct web page URLs that you may
have used to obtain literature values and supplemental
theory. Note that the reference numbers must correspond to
the reference citations used in the text of the report.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
8
LAB 2: SODIUM BOROHYDRIDE REDUCTION
PURPOSE:
You will use a reduction reaction in the synthesis of
hydrobenzoin from benzil using sodium borohydride as the
reducing agent and characterization of the product by melting
point. Your Instructor may substitute benzophenone for
hydrobenzoin in this experiment. Benzophenone (MW 182, mp 47
degrees C) would give benzhydrol (MW 184, mp 65-67 degrees C) as
the reduction product.
IMPORTANT REACTIONS:
9
C
O
C
O
Benzil
M.Mass 210
NaBH4
benzophenone
M. Mass 182.22
mp 48oC
C
OH
H
C
OH
+
H
NaBH4
H
C
OH
HO
C
H
(1R,2R)-and (1S,2S)Hydrobenzoin
mp 120oC
(1R,2S)-(meso)-Hydrobenzoin
M.Mass 214, mp 137oC
O
C
H
OH
C
benzhydrol
M. Mass 184.24
mp 65-67 oC
BACKGROUND INFORMATION:
Oxidation and reduction reactions are very important in
organic chemistry in the synthesis of desired compounds. There
are many oxidizing and reducing agents that can be used to
achieve the desired product. Some of these redox reagents are
general in that they can react with a large number of functional
groups. Other redox reagents are very specific and have limited
but specific reactivity and can cleanly do the conversion that
is desired. Sodium borohydride is such a specific reducing
reagent. It can be safely used to reduce an aldehyde or ketone
to an alcohol. Hydride type reagents are rather basic and can
often be vigorously decomposed in water or alcohol. Extreme
care should be exercised whenever you work with any type of
hydride. However, sodium borohydride is reasonably safe to use.
10
It does not undergo the decomposition as vigorously as other
hydrides. Further, the reaction can be run in alcohol and
yields are very good. The reaction that will be done in this
experiment is generally fast and almost quantitative.
EXPERIMENTAL PROCEDURE:
Dissolve 0.5 g of benzil (or benzophenone) in a 25 ml
Erlenmeyer flask using 5 ml of 95% ethanol. Slight heating may
be required but cool to room temperature before adding 0.12 g of
sodium borohydride. In about 3 minutes the reaction is complete
as noted by the disappearance of the yellow color of benzyl (if
that reactant were used). After about 5 more minutes, add 5 ml
of water and heat the solution to decompose the large excess of
sodium borohydride. While still warm, add approximately 10 ml
of water. Let the solution cool to allow the product to
crystallize. Suction filter the product, dry and weigh it and
take its melting point.
IMPORTANT INFORMATION ABOUT THE REPORT:
This experiment is another example of a synthesis reaction.
You must calculate the percent yield as you did before. Be sure
to use the correct number of moles from the balanced equation in
your calculation to determine the theoretical yield. Be sure to
record both the observed and reported melting point ranges for
your product.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 3:
OXIDATION OF BENZALDEHYDE-GREEN CHEMISTRY
PURPOSE:
This experiment will introduce the student to the new area
of Green Chemistry. Green Chemistry tries to use new reagents
or less toxic familiar reagents to be more environmental
friendly. In this experiment, dilute hydrogen peroxide and
Chlorox (which both present some hazards) will be used in place
of the more usual, more toxic dichromate reagents.
IMPORTANT REACTIONS:
11
O
O
C
C
[O]
H
OH
H2O2 or NaClO
benzaldehyde
(M. Mass 106.12
bp 178oC)
H
benzoic acid
(M. Mass 122.12
mp 121.5-122oC)
O
OH
C
benzhydrol
M. Mass 184.24
mp 65-67 oC
bleach
C
benzophenone
M. Mass 182.22
mp 48oC
BACKGROUND INFORMATION:
Green chemistry is that new aspect of chemistry in which
environmentally friendly reagents are used in place of more
hazardous traditional reagents. A great deal of research is
currently being done in this area and major success stories have
been written. Links to green chemistry web sites can be found
on Robert Shine’s web page for this course (see
www.bobshine.com).
One difficulty with green chemistry is finding reagents
that perform as well as the older reagents. It is our hope that
we will be able to introduce better experiments in this course
as future studies are done.
We can start with a simple reaction such as the oxidation
of benzaldehyde to benzoic acid. Aldehydes are very easy to
oxidize so it was thought that simple household oxidants could
be used in place of the traditional hazardous dichromate
reagents. Our study is investigating the use of dilute hydrogen
peroxide and Clorox. In the past few years at Ramapo College,
there has been success using these reagents but the yields have
been low. Your data in this experiment will be used to find the
optimum conditions for future classes to use.
12
In place of benzaldehyde, your Instructor may use
benzohydrol or acetophenone in this experiment. The green
advantage of using benzohydrol would be that it may have been
the product from the prior experiment (if your Instructor chose
that starting material) and we would be recycling reagents.
Acetophenone should be easily oxidized to benzoic acid by
hypochlorite via a haloform reaction.
Chlorox, a mild oxidant, is a dilute solution of sodium
hypochlorite (NaOCl). Chlorox should never be mixed with
ammonia solutions or ammoniated cleansers as a reaction that
releases deadly chlorine gas occurs.
The other oxidant that will be tried is dilute hydrogen
peroxide. We have found that a 3% solution that can be
purchased in a drug store is too dilute to give a meaningful
reaction. When a 10% solution was used, results were better but
still not adequate. In addition, if the 10% solution comes in
contact with the skin, it turns it white for a few hours. More
concentrated solutions exist but the hazard level rises as the
concentration is increased.
Your careful observations and well written laboratory
reports for this experiment will be very useful in determining
if this experiment could be successful in the future.
EXPERIMENTAL PROCEDURE:
The entire synthetic procedure should be carried out in the
fume hood. Although these are household chemicals, you still
need to be careful handling them. If you get any on your hands,
you will not feel it immediately, but white patches will soon
appear.
PART 1: Oxidation using Household Bleach
A: Oxidation of Benzaldehyde
Place benzaldehyde (2 mL) and glacial acetic acid (1 ml) in
a 125 mL Erlenmeyer flask, add a magnetic stirrer bar and gently
heat on a stirrer-hotplate. To the reaction mixture add
household bleach (30 mL) in approx. 5 ml portions over a 2-3
min. period. After addition is complete, heat the reaction to
approximately 80-90oC (with stirring) for 45 minutes. It is very
important that you do not allow the solution to boil. Remove the
flask from the stirrer-hotplate, allow it to cool to room
temperature. Then place it in an ice bath. Filter off the
product using a Buchner funnel, wash the product and reaction
flask with ice-cold water, and allow the solid to dry. Measure
the mass of benzoic acid produced, calculate the percent yield,
and record its melting point range.
B: Oxidation of Benzhydrol
13
Place 1.00 g of benzhydrol, 15 mL of household bleach, 15
mL of ethyl acetate and 0.100 g of tetrabutylammonium hydrogen
sulfate in a 125 mL beaker. Using a magnetic stirrer bar, stir
the mixture for 30 minutes. Remove the stir bar and the lower
aqueous layer (using a Pasteur pipette). Extract the organic
layer with 10 mL of saturated sodium chloride and then 10 mL of
water. Dry the organic layer over anhydrous sodium sulfate.
Decant or gravity filter to remove the solid drying agent and
then evaporate the organic solvent. Determine the melting point
and the percent yield of the benzophenone product.
PART 2: Oxidation using Hydrogen Peroxide
Place benzaldehyde (2 mL) and glacial acetic acid (1
ml) in a 125 mL Erlenmeyer flask, add a magnetic stirrer bar and
gently heat on a stirrer-hotplate. To the reaction mixture add
20% hydrogen peroxide (30 mL) in approx. 5 ml portions over a 23 min. period. After addition is complete, heat the reaction to
approximately 80-90oC (with stirring) for 45 minutes. It is very
important that you do not allow the solution to boil. Remove the
flask from the stirrer-hotplate, allow it to cool to room
temperature. Then place it in an ice bath. Filter off the
product using a Buchner funnel, wash the product and reaction
flask with ice-cold water, and allow the solid to dry. Measure
the mass of benzoic acid produced, calculate the percent yield,
and record its melting point range.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual
format. Be sure the percent yield calculation for each method
is carefully done. Also, record the melting point range of the
final products and compare the melting point data to the
reported melting point of benzoic acid. Using these data,
discuss the relative success of the experiment.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
14
LAB 4:
GRIGNARD REACTION
PURPOSE:
This experiment will introduce the student to the synthesis
of a sensitive organometallic intermediate (the Grignard
reagent) which is very useful in the synthesis of a large number
of different functional groups.
IMPORTANT REACTIONS:
Part 1:
Br
MgBr
+ Mg
Bromobenzene
(M. Mass 157.02, bp 156oC)
anhydrous ether
phenylmagnesium bromide
15
Part 2:
+ MgBr
-
H3O+
+
C
O
Benzophenone
(M. Mass 182.22, mp 48oC)
C
OH
Triphenylmethanol
(M. Mass 260.34, mp 164.2oC)
BACKGROUND INFORMATION:
The Grignard reaction was discovered and developed by a
French Nobel laureate in the early 1900’s. It is an example of
an organometallic compound which has a carbon magnesium bond.
Grignard reagents have been extremely useful in the synthesis of
a large number of classes of organic functional groups for the
past century. Although Grignard reagents are unstable and
decompose in air and moisture, they can be prepared and used
immediately with moderate difficulty in the undergraduate
organic chemistry laboratory. Care will need to be exercised
and the equipment must be thoroughly dried before use to insure
success. No water may enter the reaction mixture until the
final product has been synthesized.
Group IA metals (Li, Na, and K) form very basic
organometallic compounds which are very hazardous to handle.
They can be spontaneously flammable in air and react explosively
with water to release hydrogen gas. In these cases, the C-M
bond is very polar and the carbon group is highly basic,
especially in sodium and potassium compounds.
With the Group IIA metal magnesium, the C-Mg bond is not as
polar and the compound is not as difficult to handle. Yet they
are reactive enough to be very useful in synthesis. The exact
nature of the bonding in Grignard reagents has been extensively
studied in the past century and is beyond the scope of this
discussion. For the purposes of this experiment, one can
consider the bonding to be R-MgBr, where R is an alkyl or aryl
group.
Organometallic compounds with transition metals (such as,
iron, mercury, lead, tin, cadmium, and many others) have an even
more covalent carbon metal bond. Many of these compounds are
stable and often very toxic. Organic mercury compounds are
16
often mentioned as environmental hazards in the New Jersey area.
One reason for the extreme toxicity of some organometallic
compounds is the volatility that the organic group imparts on
the molecule which makes it easier for entry into the body.
Returning to the chemistry of the organomagnesium
(Grignard) compounds, they are generally prepared by the
reaction of an alkyl or aryl halide with magnesium metal
turnings. The magnesium turnings are crushed in a mortar and
pestle just before use to expose a fresh surface on the metal.
Of the halides used, iodides are best, fluorides are the least
reactive and bromides are usually preferred for their good
reactivity and reasonable cost. Grignard reagents are usually
prepared in anhydrous ether as the volatile ether solvent helps
keep air away from the reaction. It cannot be stressed enough
that the ether must be very dry and kept that way if the
reaction is to be successful. Small traces of water will
destroy the reagent or keep the reaction from starting.
Once formed, the Grignard reagent must be used immediately.
One can combine this reagent with a large number of different
functional group compounds to give a wide variety of possible
products. The Grignard reagent can react with:
1. any active hydrogen (such as water, alcohols, carboxylic
acids, etc.) to produce and alkane or arene (usually this
is not a desirable reaction).
2. formaldehyde to form a primary alcohol.
3. an aldehyde (other than formaldehyde) to form a secondary
alcohol.
4. a ketone to form a tertiary alcohol (which will be done in
this experiment).
5. an ester to form a tertiary alcohol.
6. carbon dioxide (as solid dry ice) to form a carboxylic
acid.
7. many other classes of compounds to form other useful
products.
Due to the great reactivity of Grignard reagents, the alkyl or
aryl halide starting material cannot have any reactive function
group as part of its molecule. This generally limits the halide
to be alkyl, alkenyl, alkynyl, or aryl. An ether group is also
compatible and unreactive with the Grignard reagent.
In today’s experiment, bromobenzene will react with
magnesium turnings to form phenyl magnesium bromide (the
Grignard reagent). This intermediate will then be immediately
treated with benzophenone to prepare triphenylmethanol (a solid
tertiary alcohol).
EXPERIMENTAL PROCEDURE:
17
In order to minimize the exposure of the Grignard reagent
to water, the equipment and reagents used in this experiment
must be absolutely dry. All glassware (reaction glassware, two
sample vials and a stirring rod) must be pre-dried in an oven at
110oC for at least 30 minutes prior to use. The anhydrous diethyl
ether solvent and the bromobenzene will be stored over molecular
sieves to absorb any moisture they are exposed to and the
magnesium metal will be pre-dried in an oven and crushed in a
mortar and pestle to give a fresh magnesium surface. The above
preparation work will be completed by the staff before you
arrive at the laboratory.
PART 1: Generation of Grignard Reagent
The procedure for this experiment is still being
developed and your Instructor may give directions that are
different from what follows.
Remove the first reaction vessel or test tube from the oven
and cap it with a rubber septum. Add magnesium powder or
turnings (50mg, 2 mmol) to the tube, minimizing the time that
the tube is un-capped. Carefully add anhydrous diethyl ether
(0.5 mL) to the tube using a dry syringe, injecting the needle
through the rubber septum. If a glass syringe is not available
a dried disposable glass pipette can be used instead.
Remove a sample vial from the oven and cap it with a rubber
septum. To this vial add bromobenzene (330 mg, 2.1 mmol) and
diethyl ether (0.7 mL) via the syringe as you did for the first
tube. After addition of the ether solvent, do not remove the
needle from the septum. As soon as the ether has been added to
the vial, swirl the mixture and immediately remove the entire
bromobenzene-ether mixture by carefully sucking it up into the
syringe. Once this has been done, inject approximately one third
of the bromobenzene-ether mixture into the first reaction tube
containing the magnesium metal in ether. Mix the contents and
add a pressure release needle to the septum. If the reaction
does not appear to start at this point, first remove the syringe
(if used) containing the remaining bromobenzene-ether mixture.
Carefully remove the septum and the pressure release needle and
quickly grind the magnesium metal using the oven dried glass
stirrer rod. Replace the septum and pressure release needle as
soon as possible to minimize air-water exposure. Once the
reaction starts, the clear solution will become cloudy and the
ether may begin to boil. At this point, reattach the syringe
containing the remaining bromobenzene-ether mixture and add the
rest of the solution drop wise at such a rate that the reaction
does no get out of control. Once the entire contents of the
syringe has been added, continue to agitate the reaction vessel
until the reaction is complete, which will be visible when very
little, if any, magnesium metal remains. The synthesized
18
phenylmagnesium bromide is not isolated, but will be used in
situ for part 2.
PART 2: Synthesis of Triphenylmethanol
Remove the second oven dried vial and cap it with a
rubber septum. Add benzophenone (0.364 g, 2.0 mmol) and diethyl
ether (1.0 mL) in the same manner and using the same precautions
as you did in part 1. Shake the vial to dissolve the
benzophenone and remove the resulting solution by sucking it up
into the dry syringe.
Carefully remove the syringe containing the benzophenoneether solution and inject it drop wise into the reaction tube
containing the phenylmagnesium bromide. A red color should be
observed at this point. After all the benzophenone solution has
been added, rinse the vial with a few drops of ether and inject
these washings into the reaction tube. The reaction is complete
when the red color disappears.
On completion, cool the reaction tube in ice, and very
carefully add 3 M hydrochloric acid (2 mL) drop wise with
stirring. If there is any un-reacted magnesium metal in your
reaction tube be especially careful as acids react with metals
to release hydrogen gas. This could lead to your reaction
solution bubbling out of your tube. On addition of the acid, a
two-phase system should result. Add more ether solvent if the
white triphenylmethanol product begins to crystallize out.
Carefully remove the lower aqueous layer using a Pasteur
pipette. To the remaining ether layer add an equal volume of
saturated aqueous sodium chloride solution, shake the tube,
allow the layers to settle and remove the lower aqueous layer as
before. Dry the ether layer over calcium chloride pellets for 510 minutes. Then carefully transfer the ether layer via pipette
into a pre-weighed beaker. Wash the solid drying agent with a
small amount of ether and combine the washings with the solution
in the beaker. Remove the ether solvent by carefully blowing a
stream of air over the solution in the beaker. When it appears
to be dry, re-weigh the beaker to record the mass of
triphenylmethanol produced. Then add ice-cold petroleum-ether
(1 mL) to the white residue and grind (triturate) the product
with a glass rod. Filter the product using a Hirsch funnel and
air dry the solid. Weigh the solid to record the mass of
purified triphenylmethanol obtained. Calculate the percent yield
of the final triphenylmethanol product and determine the melting
point.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual
format. Be sure the percent yield calculation is carefully
19
done. Also, record the melting point range of the final product
and compare that melting point to the reported melting point of
triphenylmethanol. Using these data, discuss the relative
success of the experiment.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 5:
DIELS-ALDER REACTION
PURPOSE:
This experiment will introduce the student to an important
cycloaddition reaction. The Diels Alder reaction is reversible
and the student will need to consider methods to increase the
yield, if possible.
IMPORTANT REACTIONS:
Diene
Dienophile
Adduct
20
H
O
H
H O
O
H
O
-phellandrene
(M. Mass 136
bp 175-176oC)
Maleic anhydride
(M. Mass 98
mp 54-56o)
O
O
endo-7-isopropyl-4-methylbicyclo[2.2.2]
oct-4-ene-1,2-dioic anhydride
(M. Mass 234, mp 126-127oC)
BACKGROUND INFORMATION:
The Diels Alder reaction is an example of a cycloaddition
reaction discovered by two German chemists (Otto Diels and Kurt
Alder) in the 1950’s. This reaction is an example of a
concerted reaction in which bonds are being made as other bonds
are being broken. Effective overlap of all bonding orbitals is
essential for the reaction to occur which leads to a specific
stereochemistry in the products. In this reaction, the endo
isomer is formed.
The Diels Alder reaction is an example of a 2-4
cycloaddition reaction in which an alkene adds in a 1,4 addition
to a diene. Neither Diels nor Alder fully understood the
generality or significance of cycloaddition reactions. This was
left for Roald Hofmann (now at Cornell University) and R. B.
Woodward from Harvard University to discover in the late 1960’s.
The Woodward Hofmann rules for cycloaddition reactions (which
are beyond the scope of this discussion) were perhaps one of the
major discoveries in organic synthesis in the 20th century.
In early work with this reaction, results were mixed and
yields varied quite a bit. Later it was found that this
reaction is reversible. If one considers LeChatelier’s rule, it
might be possible to shift the equilibrium in the desired
direction.
In the experiment that will be done here, alphaphellandrene will react with maleic anhydride. The alphaphellandrene is a natural product derived from cedar wood and
has a characteristic cedar wood odor. It is not 100% pure so
the directions call for an added amount to be used to compensate
for the impurity. Maleic anhydride is a white solid. It can
hydrolyze with water to give maleic acid so water should be
avoided if possible. With prolonged exposure to moisture, the
anhydride group in the product may convert to the diacid which
21
will have different properties. The final bicyclic product is
usually obtained without difficulty.
EXPERIMENTAL PROCEDURE:
This reaction must be done in a fume cupboard. Place maleic
anhydride (0.527 g, 5.4 mmoles) and -phellandrene (1 mL, 85 %
pure, 5.4 mmoles) into a 25 mL round bottomed flask and attach a
water-cooled condenser. Add anhydrous acetone (3 mL) through the
top of the condenser and swirl the reaction mixture. The
reaction is exothermic and a yellow color should appear at this
point. Heat the reaction under reflux for 1 hour using a steam
bath or hot water bath. After this time, carefully remove the
condenser, pour the reaction mixture into a 20 mL beaker and
allow the acetone solvent to evaporate to approximately half of
its original volume. Allow the reaction to cool to room
temperature, then cool the reaction vessel in an ice bath to
induce crystallization of the Diels-Alder adduct (scratching
with a glass rod may be required). Filter off your product using
a Hirsch funnel, washing the flask with a small amount of icecold acetone. Dry and weigh the final product, record the
melting point and determine the percent yield.
If required, (i.e. if the melting point of the product is
much lower than expected) recrystallize the product using the
minimum amount of warm methanol (be very careful to not overheat
as methanolysis of the anhydride group could occur).
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual
format. Be sure the percent yield calculation is carefully
done. Also, record the melting point range of the final product
and compare that melting point to the reported melting point of
the product given above. Using these data, discuss the relative
success of the experiment.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
22
LAB 6:
NITRATION REACTION
PURPOSE:
This experiment will introduce the student to one of the
important electrophilic aromatic substitution reactions. The
experiment uses concentrated nitric acid and concentrated
sulfuric acid so the student will need to use great care in
handling these reagents.
IMPORTANT REACTIONS:
HNO3 + 2 H2SO4
NO2+ + 2 HSO4- + H3O+
Nitronium ion
23
CO2CH3
CO2CH3
HNO3 / H2SO4
NO2
Methyl benzoate
(M. Mass 136.16, bp 199.6oC)
Methyl 3-nitrobenzoate
(M. Mass 181.15, mp 78oC)
BACKGROUND INFORMATION:
This experiment and the one next week are examples of
electrophilic aromatic substitution reactions. Aromatic systems
such as the benzene ring have enhanced resistance toward
reactions due to the stability that resonance gives to the
aromatic ring. Addition reactions are highly unlikely as they
would destroy the conjugated aromatic system. Substitutions can
occur and the best reagent to use should have electrophilic
properties as the aromatic ring is rich in electrons. The class
of reactions known as electrophilic aromatic substitution
reactions is studied extensively in the lecture part of the
course. These two experiments will show how they can be
performed in the laboratory.
There are five reactions that are normally presented when
discussing electrophilic aromatic substitution reactions. They
include:
1. nitration using concentrated nitric acid and concentrated
sulfuric acid to generate the nitronium ion electrophile
(which will be done in this experiment).
2. halogenation using a halogen and a Lewis acid to generate
the halonium ion elctrophile.
3. sulfonation using sulfur trioxide as the electrophile.
This is the only neutral electrophile in this series of
reactions and this reaction is reversible.
4. Friedel Crafts alkylation using some source of a carbenium
ion as the electrophile. This reaction will be done next
week and will use an alcohol and concentrated sulfuric acid
to generate the carbenium ion.
5. Friedel Crafts acylation using an acyl halide and a Lewis
acid to generate the acylium ion electrophile.
In the experiment that will be done today, a substituted
aromatic ring is used which will lead to meta nitration of the
ring. The substituent chosen will moderate the reaction to
avoid di- and trisubstitution of the ring which could lead to
explosive products. Trinitrobenzene is explosive. It is best
not to heat the reaction too high or too long to avoid further
undesired substitution.
24
Also note that this reaction often shows a delayed start.
It is best to be patient. If the mixture is heated highly or
longer than directed, an uncontrolled reaction may ensue. And,
if the reaction is quickly quenched in an ice bath, it may be
permanently stopped. If brown fumes start to form, the reaction
may be proceeding too quickly and should be moderated.
Concentrated nitric acid and concentrated sulfuric acid
pose a hazard when being handled. Gloves must be worn and care
must be used. If any of the acid mixture gets on the skin, it
must be immediately washed with large amounts of cold water.
Immediately wash the affected area with water if you suspect
that acid may be on your skin. Nitric acid destroys proteins
and if some of it (either as liquid or vapors) gets on the skin,
the skin cells will die over a few hours to days leaving an
orange patch on the surface. This generally wears off in a few
days.
This reaction usually goes well if care is exercised. The
final product is a crystalline solid with a low melting point.
EXPERIMENTAL PROCEDURE:
Carefully combine concentrated sulfuric acid (0.4 mL) and
concentrated nitric acid (0.4 mL) in a suitable test tube or
vial and place it in an ice bath. To a second test tube or vial,
add methyl benzoate (0.6 g, 4.4 mmoles) and concentrated
sulfuric acid (1.2 mL), flick the container to mix the
components of this viscous mixture, and then cool it in an ice
bath as well. Using a glass Pasteur pipette, carefully add the
sulfuric-nitric acid mixture drop wise to the methyl benzoate
solution, using a glass stirring rod to mix the reaction. On
complete addition of the acid mixture, remove the reaction from
the ice bath, allow it to warm up to room temperature, and let
is stand for 15 minutes. After this time, in order to
crystallize the product, pour the mixture into a small beaker
that contains approximately 5g of ice. Filter the resulting
solid using a Hirsch funnel and wash out the reaction tube with
ice-cold water. When all the product has been transferred to the
filtration funnel, wash the product with ice-cold methanol (0.5
mL). Record the mass and melting point of this crude product and
calculate the percent yield. Recrystallize the product using an
equal mass of methanol and re-record the mass, melting point and
percent yield of the pure product.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual
format. Be sure the percent yield calculation is carefully
done. Also, record the melting point range of the final product
and compare that melting point to the reported melting point of
25
methyl 3-nitrobenzoate. Using these data, discuss the relative
success of the experiment and discuss whether there is any
evidence polysubstitution occurred.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 7:
FRIEDEL-CRAFTS ALKYLATION REACTION
PURPOSE:
This experiment will introduce the student to a Friedel
Crafts alkylation reaction, another one of the important
electrophilic aromatic substitution reactions. The experiment
uses concentrated sulfuric acid to generate an unstable
carbenium ion.
IMPORTANT REACTION:
26
CH3
OMe
CH3
+ 2
MeO
H2SO4
H3C C CH3
OMe
H3C C OH
CH3
MeO
H3C C
CH3
CH3
1,4-dimethoxybenzene
(M. Mass 138.16
mp 57oC)
2-methyl-2-propanol
(M. Mass 74.12
bp 82.8oC)
1,4-di-t-butyl-2,5-dimethoxybenzene
(M. Mass 250.37, mp 104-105oC)
BACKGROUND INFORMATION:
The Friedel Crafts reaction, named in honor of its two
founders, is another example of an electrophilic aromatic
substitution reaction. Two variations exist - an alkylation
using a carbenium ion and an acylation using an acylium ion. In
this experiment, an alkylation will be performed. Any source of
a carbenium ion can be used in a Friedel Crafts alkylation
reaction. Historically, alkyl halides were treated with the
Lewis acid, aluminum trichloride. The current experiment will
use an alcohol in concentrated sulfuric acid. One could also
use an alkene with sulfuric acid.
The Friedel Crafts alkylation reaction has many problems
that make the acylation reaction (followed by a Clemmensen or
Wolff-Kishner reduction) a better choice. However, by carefully
choosing the reagents in this experiment the problems were
minimized.
The three main difficulties involve the activity of the
ring, the possibilities of carbenium ion rearrangement, and
further activation of the ring by the adding alkyl groups. By
choosing t-butyl alcohol in this experiment, rearrangement of
the carbenium ion is not a factor as the tertiary carbenium ion
that is generated will not rearrange. The activity of the
benzene ring is enhanced by the addition of two methoxy groups.
The bulky t-butyl groups stop the polyaddition at
disubstitution. You may want to further ponder the choice of
reagents in this reaction which gives a good yield of only one
isomer compared to many possible isomers in normal alkylation
reactions.
EXPERIMENTAL PROCEDURE:
Place 1,4-dimethoxybenzene (0.300 g, 2.2 mmoles) and
acetic acid (1 mL) in a suitable test tube or vial (not microscale) and, if needed, gently warm to dissolve. Add pre-melted
27
t-butyl alcohol (0.5 mL) to this tube and cool the entire
mixture in an ice bath. Carefully add concentrated sulfuric acid
(1 mL) drop wise via a glass pipette, mixing the solution with a
glass rod after each drop. A solid product may be visible at
this point, but in order to complete the reaction, remove the
reaction vessel from the ice-bath, allow it to warm to room
temperature, and let it stand for 10 minutes. After this time,
re-cool the tube in ice in order to induce complete
crystallization. At this point, very carefully add water (5 mL)
drop wise to the mixture in the reaction vessel, stirring after
the addition of each drop. Filter off the product using a Hirsch
funnel and wash the solid with ice-cold water. You could also
further wash the crystals in the Hirsch funnel with cold
methanol to purify it. After drying, record the mass and
melting point of the crude product and determine the percentage
yield. If needed, recrystallize the product in the minimum
amount of hot methanol, and determine the mass, melting point
and percent yield of the purified product.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual
format. Be sure the percent yield calculation is carefully
done. Also, record the melting point range of the final product
and compare that melting point to the reported melting point of
1,4-di-t-butyl-2,5-dimethoxybenzene. Using these data, discuss
the relative success of the experiment.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 8:
PART A: QUALITATIVE ANALYSIS OF ALDEHYDES AND KETONES
PURPOSE:
This experiment will introduce the student to
organic analysis. A number of test tube reactions
to identify an aldehyde and/or a ketone unknown in
computer simulation program called Sim-Org will be
homework assignment in Part B.
qualitative
will be done
Part A and a
used as a
IMPORTANT REACTIONS AND DATA:
28
Part 1: Tollen's Test
O
O
+ 2 Ag(NH3)2OH
C
R
+ 2 Ag + 3 NH3 + H2O
C
H
O-NH4+
R
Silver
Mirror
Aldehyde
Part 2: Iodoform Test
O
+
C
R
O
3 I2 + 4 OH-
+ CHI3 + 3 I- + 3 H2O
C
CH3
O-
R
Iodoform
methyl ketone
Part 3: 2,4-Dinitrophenylhydrazones
O2N
O
+
C
R
R'
N
R
H+
H2N
O2 N
C
NO2
N
N
R'
H
NO2
H
2,4-dinitrophenylhydrazine
2,4-dinitrophenylhydrazone
Part 4: Semicarbazones
O
+
C
R
R'
ClH 3 +N
O
N C
H
NH2
semicarbazide
hydrochloride
N
R
C
- H2O
O
N
N
R'
C
H
NH2
+
N+ClH
semicarbazone
29
LAB 8: Table of Unknown Aldehydes and Ketones
Compound
2-heptanone
3-heptanone
n-heptanal
n-butanal
Acetone
3-pentanone
Benzaldehyde
Acetophenone
Cinnamaldehyde
Hexane-2,5-dione
Mpt of 2,4-DNP
89
81
108
123
126
156
237
238
255
257
Mpt of
semicarbazone
123
101
109
95-106
187
138
222
198
215
224
BACKGROUND INFORMATION:
This experiment will be the first of a few experiments that
will explore qualitative organic analysis. Analysis of unknown
compounds is routinely done by chemists and occupies much of the
time expended by scientists. Analytical chemistry is an entire
separate study which, by its very nature, crosses into other
branches such as organic chemistry. Analytical chemistry can be
qualitative (interested only in the identification of an
unknown) or quantitative (interested in the nature and
percentage composition of unknowns). Of the two, qualitative is
less demanding. Qualitative analysis may use instruments or
classical wet chemical test tube reactions. Instrumental
analysis was introduced last semester in the discussions on
infrared and proton magnetic resonance spectroscopy. Wet
chemical analysis was also presented in the experiment that
studied Sn1 and Sn2 reactions. This experiment will expand on
that brief introduction last semester.
Wet chemical analysis usually involves using simple and
quick test tube reactions that have clear observations.
However, since many factors can affect the result, the observer
must look beyond the observation and carefully interpret the
data in making a decision about the identity of an unknown.
Reactions that quickly give a precipitate, color change or gas
evolution are ideally suited for qualitative tests.
Usually, in organic chemistry a qualitative test only
identifies the functional group class to which the unknown
belongs. Further work must be done to fully determine the exact
identity of the unknown compound. This later aspect of
qualitative organic analysis is called ‘making a derivative’.
30
In today’s experiment there are four tests. The first two
(Tollen’s test and iodoform reaction) are used to get a general
class of possibilities. The last two (2,4dinitrophenylhydrazone
formation and semicarbazone formation) are used to make
derivatives. Actually, in the broader scheme of qualitative
organic analysis, the 2,4-dinitrophenylhydrazone reaction
identifies the class and makes a derivative. However, since we
know that today’s unknowns are aldehydes or ketones, this test
does not supply any useful differentiation as it is positive for
both these classes.
The Tollens test gives a precipitate of silver metal
(either as a beautiful silver mirror on the inside of the test
tube or a black precipitate of colloidal silver) if the unknown
is an aldehyde. This mild oxidizing agent can also give a
positive test for any very easily oxidized organic compound such
as some carbohydrates. Further note that an insoluble unknown
aldehyde may give a false negative test if the reagents are not
mixed thoroughly.
The iodoform test gives a light yellow precipitate of
iodoform if the unknown has a methyl carbonyl group as part of
the molecule. Since the reagent is also mildly oxidizing, a
methyl group next to a secondary alcohol group will give a
positive test. The test is positive for 2-pentanone, acetone,
2-butanone, ethanol, 2-propanol and like compounds. The test is
negative for 3-pentanone, for example. The iodoform that forms
has a melting point of 117 degrees but cannot be used as a
derivative as it is the same product no matter what the unknown
is.
The formation of a 2,4-dinitrophenylhydrazone is a messy
reaction. Sulfuric acid is one of the ingredients in the test
reagent. The precipitate is difficult to filter and dry. Some
success in cleaning the product can be achieved by washing the
solid with cold ethanol. Since percent yields of derivatives
are never an issue, loss of material is acceptable if a purer
solid results. Sometimes, the color of the
2,4dinitrophenylhydrazone (2,4-DNP for short) can give some
information about the unknown. Highly conjugated carbonyl
groups give deep red 2,4-DNP derivatives while non conjugated
carbonyl groups give yellow 2,4-DNP compounds.
The formation of a semicarbazone derivative is a nice
second choice in identifying an unknown. Since precipitation
can be difficult it is usually not a first choice.
Considering the table of data above, if the unknown were 3pentanone and a successful 2,4-DNP was prepared with a melting
point of, say, 153 degrees, there would be no need to make a
second derivative as this melting point would uniquely identify
the unknown from this list of possibilities.
However, if the
31
unknown were acetone, the 2,4-DNP would not clearly rule out nbutanal as their 2,4-DNP derivatives have similar melting
points. A semicarbazone would clearly identify what the unknown
would be in this case. However, other data would help
distinguish acetone from n-butanal. A Tollen’s test would be
positive for n-butanal and the iodoform test would be positive
for acetone. So, the final identification of an unknown is
achieved by an analysis of the data available rather than
following a rigid set of rules or procedures.
EXPERIMENTAL PROCEDURE:
Your goal is to identify the unknown aldehyde or ketone
sample assigned to you from the table. The tests in parts 1 & 2
will enable you to narrow your search to a particular type of
compound, and measuring the melting points of the derivatives
you synthesize in parts 3 & 4 will give the identity of a
particular aldehyde or ketone.
PART 1: Tollens Test
This test must be performed on three samples: a known
aldehyde (postive test), a known ketone (negative test) and your
unknown sample.
Clean three test tubes by adding sodium hydroxide solution
(2 mL) to them and heating them in a water bath.
To prepare the Tollens reagent, place a 0.03 M solution of
silver nitrate solution (2 mL) into a 10 ml volumetric flask and
add a 3 M of sodium hydroxide solution (1 mL) to produce a
grayish suspension of silver oxide. To this, add a 2.8 %
solution of ammonia (0.5 mL) dropwise with shaking. If the
precipitate does not dissolve, add more ammonia dropwise until
it does to a maximum of 3 mL. Then dilute the entire mixture to
10 mL total by addition of water. The Tollens reagent can form
explosive compounds on standing and should not be stored.
Remove the sodium hydroxide solution from your three test
tubes, rinse them with water, and add your freshly prepared
Tollens reagent (1 mL) to each of the tubes. To the first tube
add one drop of your known aldehyde, to the second tube add one
drop of your known ketone and to the third tube add one drop of
your unknown. Allow the tubes to stand for several minutes and
look for the appearance of a silver mirror coating on the inside
of the tube. If no precipitate has formed, heat the test tube
in a warm water bath for a few minutes.
PART 2: Iodoform Test
This test must be performed on three samples: a known
methyl ketone (postive test), a non-methyl ketone (negative
test) and your unknown sample.
32
Place the sample to be tested (approximately 50 mg or three
drops) in a test tube and dissolve it in water (2 mL). (If it
does not dissolve in water, repeat the procedure and dissolve it
in 2 mL of 1,2-dimethoxyethane instead). Add 3 M sodium
hydroxide solution (2 mL) followed by the careful addition of
the iodoform solution (3 mL). For a positive test with a known
methyl ketone, the iodoform reagent’s color should disappear and
the yellow iodoform product separates. Repeat the procedure for
a known non-methyl ketone and your unknown.
PART 3: 2,4-Dinitrophenylhydrazone
Place the 2,4-Dinitrophenylhydrazine solution (5 mL)
in a test tube and add approximately 50 mg (or three drops) of
your unknown sample. Heat the sample tube in a water bath for
several minutes until the presence of a precipitate is observed.
Then cool the reaction tube in an ice bath and filter off the
product using a Hirsch (or perhaps a Buchner funnel would be
better) funnel. Wash the product and the test tube with ice-cold
water, and then wash the product with ice-cold ethanol and allow
the solid to dry thoroughly. Record the melting point range of
your product.
PART 4: Semicarbazone
Place the semicarbazide hydrochloride solution (0.5
mL) in a test tube and add approximately 100 mg of your unknown
sample. To this add methanol (1 ml) and pyridine (10 drops, use
in a fume hood), then heat the sample tube in a water bath for
10 minutes. Cool the reaction tube in an ice bath and allow the
product to crystallize (you may need to scratch the tube with a
glass rod to induce crystallization). Filter off the product
using a Hirsch funnel and wash the product and the reaction tube
with ice-cold water. Finally, wash the product with ice-cold
methanol and allow it to dry thoroughly. Record the melting
point range of your product.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will be different from the
usual format of the past few experiments. No percent yield
calculation will be done. Melting point ranges of any
derivatives must be recorded and compared to the melting points
given in the table to determine the identity of any unknown.
The identity of any unknown and its unknown number should be
given along with conclusive evidence that supports the claim
that is made.
END OF LABORATORY EXPERIMENT PART A (SEE PART B ON NEXT PAGE).
33
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 8:
PART B: SIM-ORG SOFTWARE HOMEWORK ASSIGNMENT
PURPOSE:
The student will use a computer simulation program called
Sim-Org developed at Ramapo College to learn a great deal about
qualitative organic chemistry. After some practice with the
software, the student will be asked to do a number of unknown
analyses. This assignment will be done on your own time in the
next few weeks. The program may be run on any computer on
campus. It is not available on the internet. Exact
instructions about this assignment and how to run the program
will be given to you. Also, see Appendix A at this time to see
a longer, more informative version of the Program Help section
which appears below.
BACKGROUND INFORMATION:
QUALITATIVE ORGANIC ANALYSIS
SIM-ORG PROGRAM HELP SECTION
SHORT VERSION
SEE APPENDIX A FOR LONG VERSION
Dr. Scott Frees and Dr. Robert Shine and Jeffrey Ludwig
34
Ramapo College of New Jersey
Mahwah, NJ 07430
CONTENTS:
Introduction
Solubility Classification
Functional Group Classification Tests
Derivative Formation and Use
Final Identification of an Unknown Substance
INTRODUCTION
There are two methods for identifying the structure of an
unknown organic compound. The first and older method is to run
classification tests to identify the functional group of the
compound followed by the production of one or more derivative
compounds to confirm the exact nature of the unknown. The
second method is to determine the spectral properties of the
unknown using mainly infrared and proton magnetic resonance
spectroscopy. The first method will be covered in this
simulation program. This program has 12 different functional
group classes and 500 different unknowns. There are 22
different classification tests to determine the functional group
of the unknown. There are 21 different derivatives to help
identify the exact name for the unknown. Since this program is
still under development as this manual is being printed, special
instructions for the use of Sim-Org will be given as a handout
when the assignment is presented.
The general method to determine the identity of an unknown
substance by classical methods is to gather some introductory
information about the compound. Note the odor, color, and
melting or boiling point of the material. Then find its
solubility characteristics by doing a solubility classification
as described below. From the information obtained from the
solubility classification run appropriate functional group
classification tests to identify the group to which the unknown
belongs. Then the unknown is converted into one or more
different solids called derivatives. Consulting tables of
derivative melting points one can then identify the exact
identity of the unknown compound.
In order to intelligently conduct the functional group
classification tests a solubility classification is usually done
first to narrow down the possible functional group
possibilities.
A problem may arise when an unknown substance has two or
more functional groups in the molecule. This may lead to
35
confusion when interpreting the functional group and could lead
one to the wrong table of derivatives. Such unknowns are more
difficult to identify. There are a few such compounds in this
simulation program.
SOLUBILITY CLASSIFICATION
The solubility of an organic compound in various solvents
can give valuable information about the unknown. The general
rule of 'like dissolves like' or 'polar compounds dissolve more
readily in polar solvents' is useful. Also, organic acids (such
as carboxylic acids and phenols) react with bases to form water
soluble salts and organic bases (such as amines) react with
acids to form water soluble salts. It should be noted that the
polarity of an organic compound is increased by the kind and
number of polar functional groups in the molecule and that the
polarity decreases as the size of the non polar aliphatic group
in the molecule increases.
With this background, one begins the solubility
classification by adding 3 drops or 3 mg of the unknown to 3 ml
of water and shaking the mixture. If the unknown dissolves, it
is a polar compound and is placed in solubility group S1. An
unknown in class S1 is then tested as above using ether as the
solvent. If it dissolved in both water and ether it is then
placed in class S2. For unknowns that do not fall into either
class S1 or S2, the unknown’s solubility in 5% sodium
bicarbonate is determined. If it is soluble, the unknown is
placed in class A1. If it is not soluble, the solubility in 5%
sodium hydroxide is studied. If it is soluble at this point,
the unknown belongs in class A2. If an unknown is insoluble to
this point it is next tested for solubility in 5% hydrochloric
acid. Compounds soluble in 5% hydrochloric acid are placed in
solubility class B1. For compounds insoluble to this point the
next solvent to try is concentrated sulfuric acid. Unknowns
soluble in only this acid are placed in solubility class N1.
A
further distinction can be made for compounds soluble in
concentrated sulfuric acid by testing their solubility in 85%
phosphoric acid. Such compounds that are soluble in 85%
phosphoric acid are placed in class N2. Finally, for compounds
insoluble to this point are paced in class IN.
These solubility classes and their consequences can be
summarized below:
S1
These are very polar compounds which consist of salts of
carboxylic acids or amines. It is also possible the compound is
of low molecular weight and has many polar functional groups
such as a carbohydrate.
36
S2
These compounds are low molecular weight (generally less
than 5 carbons) with a polar functional group such as carboxylic
acid, amine, alcohol, aldehyde, or ketone.
A1
Higher molecular weight carboxylic acids fall into this
class.
A2
Phenols show this kind of solubility.
B1
Primary, secondary and tertiary amines fall into this
class. However, if there are two or more phenyl groups on the
nitrogen, the amine will probably not be basic enough to form
the salt and will, then, be insoluble.
N1
These are higher molecular weight compounds (generally more
than 9 carbons) containing an oxygen atom.
N2
These are medium size molecules (generally containing from
5 to 9 carbons) containing an oxygen atom.
IN
These are neutral compounds. Alkyl halides and alkanes
fall into this class.
The results of a solubility classification should not be
strictly interpreted as there are many overlaps. Use the
results of this classification only as a focus into which
classification tests should be done first.
FUNCTIONAL GROUP CLASSIFICATION TESTS
Below are listed 22 chemical tests that could be used to
help identify an unknown. The tests are listed in
numerical/alphabetical order.
1. 2,4-dinitrophenylhydrazone
2. Acetyl chloride
3. Basic hydrolysis
4. Beilstein
5. Benedict
6. Bromine in carbon tetrachloride
7. Ceric nitrate
8. Chromic acid
9. Combustion
10. Ferric chloride
11. Ferric hydroxamate
12. Ferrous hydroxide
13. Hinsberg
14. Hydroxylamine hydrochloride
15. Iodoform
16. Lucas
17. Nitrous acid
18. pH in ethanol/water
19. Potassium permanganate
20. Silver nitrate in ethanol
21. Sodium fusion
37
22.
Tollens
DERIVATIVE FORMATION AND USE
Below are listed 21 derivatives that could be prepared from
various unknowns to help in a final determination of the
unknown. The derivatives are listed in numerical/alphabetical
order.
1. alpha-naphthylurethane
2. 2,4-dinitrophenylhydrazone
3. 3,5-dinitrobenzoate
4. Acetamide
5. Acid from hydrolysis
6. Amide
7. Anilide
8. Benzamide
9. Benzenesulfonyl chloride
10. Bromo derivative
11. Methiodide
12. Neutralization equivalent
13. Oxime
14. Phenylhydrazone
15. Phenylurethan
16. Picrate
17. p-Nitrobenzyl ester
18. p-Nitrophenylhydrazone
19. p-Toluenesulfonamide
20. p-Toluidide
21. Semicarbazone
FINAL IDENTIFICATION OF AN UNKNOWN SUBSTANCE
Tables of organic substances can be used to identify the
unknown based on the results of the classification tests and the
derivative melting point results that you obtained.
TABLES OF UNKNOWNS - Once the derivative melting point data have
been recorded enter the Tables of Unknowns by selecting the
suspected functional group class. Here a list of organic
compounds separated by type will appear. Select the family that
the unknown belongs to. A list of all the compounds of that
type, presented in order of increasing boiling/melting point
will appear. Also listed are the melting points of any
derivatives that can be synthesized from the class of the
unknown compound. By matching the table data with the unknown
compound data obtained above, one can identify the unknown.
ANSWER TRIAL - Based on all the melting point data in the Tables
of Unknowns, one will now have an idea of what the unknown
38
sample is. To see if you are correct, you can enter it into the
program by selecting Answer Trial. Make sure that you select the
compound correctly, exactly as it appears in the table of
unknowns. If you are correct, a congratulation message will
appear. If you are wrong, first re-check your data for the
unknown. If it is still incorrect, then you will need to go back
into the program in order to correctly identify the unknown
sample.
IMPORTANT INFORMATION ABOUT THE REPORT FOR THIS ASSIGNMENT:
You will be assigned a number of unknowns to determine using the
Sim-Org software. For your report, be sure to identify the
unknown number and compound name for each unknown.
After you
give the name of the unknown, be sure to carefully and
completely describe how you reached your decision. Tell the
tests you did to determine the identity of the compound and how
you eliminated other possibilities.
END OF SIM-ORG ASSIGNMENT.
© 2009 STEPHEN ANDERSON, SCOTT FREES AND ROBERT SHINE
39
LAB 9:
PART A: ALDOL CONDENSATION REACTION
PURPOSE:
These experiments will introduce the student to one of the
many condensation reactions in Organic Chemistry. These two
syntheses (Part A and Part B) usually give good yields with
little difficulty. Both can be completed within one lab period
IMPORTANT REACTION:
2
O
O
C
C
H
Benzaldehyde
(M.Mass 106.13
bp 178oC)
+
H3C
NaOH
CH3
Acetone
(M.Mass 58.08
bp 56oC)
O
H H
C C C C C
H H
dibenzalacetone
(M.Mass 234.30
mp 110.5-112oC)
BACKGROUND INFORMATION:
The aldol addition reaction is one in which two aldehyde
molecules react with one another to give a product which
contains both an aldehyde and alcohol function group, hence the
name ‘aldol’. A molecule of water can easily be lost from this
product giving a conjugated alpha-beta unsaturated aldehyde. If
this dehydration occurs, the reaction is called a condensation
reaction. The overall reaction in that case would be called an
aldol condensation. There are very many variations of reactions
that seem to have an aldol flavor and such reactions are often
called aldol reactions even though they are technically
different. The reaction in this experiment is really a ClaisenSchmidt reaction because it is a reaction of an aldehyde with a
ketone. Aldol type reactions will be thoroughly presented in
the lecture part of this course.
40
This broad class of reactions has a common mechanism. One
of the molecules has a mildly acidic hydrogen which can be
removed by a strong base to give a carbanion. The resulting
carbanion acts like a nucleophile and attacks a partially
positively charged carbon in a second molecule. The negative
charge on this addition product is removed in some way depending
on the nature of the starting molecules. One way would be to
add a proton. Another would be to eliminate an anion.
Aldol and related reactions are extremely important in
organic synthesis as they allow the chemist to construct larger
molecules from smaller ones. In these reactions, a carboncarbon bond is formed. Also of great importance is that the
product molecule can have many different useful functional
groups which can be transformed in subsequent reactions to other
useful products.
The strength of the base that is used is determined by the
acidity of the active hydrogen compound. Often the base of
choice is sodium hydroxide or sodium ethoxide which are
effective in removing a hydrogen that has a pKa in the 17-20
range. The alpha hydrogen to a carbonyl or ester group often
has such a pKa due, in part, to the resonance stabilization of
the resulting anion.
In the first experiment to be done today, the alpha
hydrogen on an acetone molecule is removed by the hydroxide ion
giving a carbanion which attacks the carbonyl of a benzaldehyde
molecule. A hydrogen ion then adds to neutralize the adduct. A
water molecule is lost from this adduct to extend the conjugated
system. Remember that conjugated systems increase the stability
of a compound. An alpha hydrogen on the other methyl group of
the acetone molecule repeats the process described above with a
second benzaldehyde molecule giving the final product,
dibenzalacetone. Two molecules of water are formed as products
in this reaction. The final product is a nicely crystalline
yellow solid.
EXPERIMENTAL PROCEDURE:
Place sodium hydroxide (2.5 g) in a 100 mL Erlenmayer flask
and add water (25 mL) and ethanol (20 mL). Add a magnetic
stirrer bar and stir until all the NaOH has dissolved. To a
second reaction vessel, add benzaldehyde (2.65 g, 0.025 mol) and
acetone (0.725 g, 0.0125 mol). Add approximately half of the
aldehyde-ketone solution to the sodium hydroxide solution, and
stir for 10 minutes with a watch glass covering the top of the
flask. After this time, add the remainder and stir for a further
10 minutes. Filter off the product using a Buchner funnel and
wash the product with water until the washings no longer appear
to be basic (test using pH paper). The best way to do this is to
41
remove the vacuum tube from the filter flask, fill the Buchner
funnel with water, carefully stir the product with a glass rod
and re-apply the vacuum. Each time the funnel is filled with
water, add some litmus paper to the solution to test the pH.
When all traces of NaOH have been removed via water washing, dry
the product and record the mass and melting point of the crude
product. Then calculate the percent yield. Recrystallize the
product from the minimum amount of hot ethanol, recording the
mass, melting point and percent yield of the pure product.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual format
for synthesis experiments. Be sure the percent yield
calculation is carefully done. Be sure to pay attention to the
coefficients in the balanced equation when determining which
starting material is the limiting reagent. Record the melting
point range of the final product and compare that melting point
to the reported melting point of dibenzalacetone. Using these
data, discuss the relative success of the experiment.
END OF PART A EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 9:
PART B: A SOLVENT-FREE ALDOL REACTION
PURPOSE:
This experiment is yet another example of a condensation
reaction. Avoiding the use of a solvent is one of the
techniques used by the Green Chemistry method.
IMPORTANT REACTION:
O
O
C
C
CH3 +
NaOH
H
CH3
Acetophenone
(M.Mass 120.15
bp 202oC)
H
O
para-methylbenzaldehyde
(M.Mass 120.15
bp 204-205oC)
-H2O
C
C
C
H
CH3
4-methylbenzylideneacetophenone
(M.Mass 222.3
mp 93-94.5oC)
BACKGROUND INFORMATION:
42
This experiment is a condensation reaction similar to the
one done above. The synthesis of the unsaturated ketone will be
achieved by the reaction of a ketone with an aldehyde using
sodium hydroxide as the base. The difference will be that no
solvent will be used in this reaction. The reduction in the
amount of hazardous waste that is generated in a given process
is one of the methods used in Green Chemistry. Elimination of
the solvent should reduce the quantity of hazardous waste.
Usually, solvents are needed to give mobility to the
reagents so that the reacting molecules can collide and then
react with one another. Reactions between solid materials go
slowly if at all. Normally the solvent used in a reaction must
be removed when the desired product is being purified. This
generally results in the generation of more hazardous waste than
is necessary.
The choice of reagents in this reaction provides some
mobility on their own. The two reacting molecules are both
liquids. However, the necessary base, sodium hydroxide, is a
solid and must touch the acetophenone molecule to remove the
alpha hydrogen on the methyl group. This will be achieved by
grinding all three reagents together in a mortar and pestle.
The generation of an equimolar amount of water as a product of
the reaction will give some added mobility to the reactants.
The product is a solid material which makes its isolation from
the reaction mixture easier.
One thing to note in the work up procedure of this
experiment is that water is added to the solid product until the
solution does not have a basic pH. Be sure to record the
approximate amount of water you will need to reach a neutral pH.
If much water is used the Green Chemistry aspect will be
lessened. In your report, comment on how successful this
reaction is from a Green Chemistry perspective. How much waste
was generated and how hazardous was that waste? What could be
done to treat the waste to reduce its volume or make it less
hazardous?
EXPERIMENTAL PROCEDURE:
Place para-methylbenzaldehyde (0.5 g, 4.2 mmol),
acetophenone (0.5 g, 4.2 mmol) and sodium hydroxide (0.18 g, 4.5
mmol) into a mortar and grind the components together for 5
minutes. After this time, add a small amount of water to the
mortar to aid in the transfer of the yellow product to a Hirsch
funnel. Wash the product with as little water as possible until
the washings no longer appear to be basic. The best way to do
this is to remove the vacuum tube from the filter flask, fill
the Hirsch funnel with water, carefully stir the product with a
glass rod and re-apply the vacuum. Each time the funnel is
43
filled with
solution to
removed via
and melting
yield.
water, dip the end of a piece of litmus paper to the
test the pH. When all traces of NaOH have been
water washing, dry the product and record the mass
point of the product. Then calculate the percent
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will simply be a separate
results and discussion section. Be sure the percent yield
calculation is carefully done. Record the melting point range
of the final product and compare that melting point to the
reported melting point of 4-methylbenzylideneacetophenone.
Using these data, discuss the relative success of the experiment
in your discussion section.
END OF PART B EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
44
LAB 10:
WILLIAMSON ETHER SYNTHESIS
PURPOSE:
This experiment is an example of the Williamson ether
synthesis which follows the Sn2 mechanism. Here, one analgesic
will be converted into another analgesic.
IMPORTANT REACTION:
H
N
O
C
O
H
CH3
+
C
CH3
CH3CH2I
OH
acetaminophen
M. Mass 151.16
mp 168-172oC
N
OCH2CH3
ethyl iodide
M. Mass 155.98
bp 72 oC
phenacetin
M. Mass 179.22
mp 134 oC
BACKGROUND INFORMATION:
There are many over-the-counter non prescription
medications to reduce pain (analgesic), reduce fever
(antipyretic) and reduce inflammation. Salicylic acid, obtained
for willow tree bark, was used more than 100 years ago for its
medicinal properties. Since it had undesirable side effects,
much early research was done to find a better alternative. The
Bayer Company in Germany found that, by acetylating salicylic
acid, a better pain reliever was obtained. This compound,
acetylsalicylic acid, is well known as aspirin.
Over the years, many different kinds of NSAIDs (non
steroidal anti inflammatory drugs) were developed. These
include aspirin, acetaminophen, ibuprofen and naproxen sodium.
While much research has been done in developing these
profitable drugs, much still needs to be done to fully
understand the biochemical cause of pain and how pain can be
relieved. Pain relief and drug dependence is another area of
active research.
EXPERIMENTAL PROCEDURE:
45
Add 1.300 g of acetaminophen, 2.500 g of powdered anhydrous
potassium carbonate, 15.00 mL of methyl ethyl ketone, and 1.800
g of ethyl iodide carefully to a 50 mL round bottom flask. Heat
the mixture under reflux for 1 hour. After cooling, add 15 mL
of diethyl ether to the flask and transfer the reaction mixture
to a separatory funnel. Extract with two 10 mL portions of 5%
NaOH to remove unreacted acetaminophen. Dry the organic layer
with anhydrous sodium sulfate. Separate the drying agent from
the solution by decantation or gravity filtration through a
cotton plug. Evaporate the solvent. Weigh the crude product,
calculate the percent yield and obtain its melting point.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual format
for synthesis experiments. Be sure the percent yield calculation
is carefully done. Record the melting point range of the final
product and compare the experimental value to the reported
melting point of phenacetin. Using these data, discuss the
relative success of the experiment.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 11:
ANALYSIS OF CARBOHYDRATES
PURPOSE:
46
Continuing with the techniques of qualitative organic
analysis, the student will do test tube experiments to learn
about the different classes of carbohydrates and natural
sweeteners.
IMPORTANT STRUCTURES:
Monosaccharides
Aldohexose:
CHO
CHO
CHO
HO
H
H
HO
H
HO
H
OH
H
OH
H
OH
H
HO
H
H
OH
HO
H
H
OH
H
CH2OH
CH2OH
D-Mannose
OH
OH
CH2OH
D-Galactose
D-Glucose
Aldopentose:
Ketohexose:
CH2OH
CHO
O
H
HO
OH
H
H
OH
H
OH
CH2OH
D-Fructose
HO
H
H
OH
CH2OH
D-Xylose
47
Disaccharides
Lactose (from galactose and glucose, shown in aldehyde form)
OH
CH2OH
OH
O
HO
CHO
O
HO
CH2OH
OH
OH
Maltose (from 2 glucose units, shown in aldehyde form)
CH2OH
O
HO
CH2OH
HO
OH
O
OH
CHO
HO
OH
Sucrose (from glucose and fructose)
CH2OH
O
CH2OH
HO
HO
O
OH
OH
O
CH2OH
OH
BACKGROUND INFORMATION:
Sweetening the foods and drink humans consume is very
important to the food chemist. Natural caloric sweeteners have
been known for many centuries. Within the last century there
has been a growing importance to reduce the calories humans
consume to control weight. A few successful non-caloric
48
sweeteners have been developed and reached commercial
importance. The first of these to be introduced around the
1950’s was calcium cyclamate. This product was abruptly taken
off the market in the late 1960’s when a connection between its
use and bladder cancer was shown. Another artificial sweetener
developed around that time and still in use is saccharin. This
successful sweetener leaves an unpleasant after taste in some
people so it is not an ideal substitute. During the 1980’s
aspartame (Nutrasweet) was introduced. This sweetener is a
methyl ester of an amino acid dimer. It has been very
successful. The latest artificial sweeter is a chlorinated
sucrose molecule which is found in sucralose (Splenda). The
above mentioned compounds are not carbohydrates. They are
artificial sweeteners.
Carbohydrates are polyhydroxy aldehydes or ketones or
compounds that can be hydrolyzed to polyhydroxy aldehyles or
ketones. Carobhydrates which contain one carbonyl group or
potential carbonyl group (which would result from the hydrolysis
of a hemiacetal linkage) are called monosaccharides.
Monosaccharides generally contain 4 to 7 carbon atoms. When two
monosaccharide molecules bond together via an acetal or
hemiacetal linkage, a disaccharide is formed. Three
monosaccharide molecules would give a trisaccharide, etc. If a
very large number of monosaccharide molecules join together, a
polysaccharide (such as: cellulose, starch or glycogen) is
formed. These larger molecules can be split apart into the
simpler units via acid hydrolysis or enzymatic action. The
lower molecular weight carbohydrates (mono, di and
trisaccharides) are often sweet to varying degrees and are often
called sugars.
Monosaccharides can be further classified by the number of
carbon atoms in the molecule. The nomenclature ending suffix
for carbohydrates is -ose. A five carbon monosaccharide would
be a pentose; a six carbon one would be a hexose, etc. If the
carbonyl group is an aldehyde, the monosaccharide is a aldose.
The ketone containing monosaccharides are ketoses. The six
carbon aldehyde sugar known as glucose is an example of an
aldohexose. With 4 chiral centers in this molecule, glucose has
16 stereoisomers. This number rises to 32 when glucose forms an
intramolecular hemiacetal ring.
Carbohydrates can also be classified as reducing or
nonreducing. If the carbohydrate can be easily oxidized, it is
a reducing carbohydrate. If not, it is a nonreducing
carbohydrate. Reducing carbohydrates have an aldehyde group or
a hemiacetal linkage.
Since carbohydrate molecules contain a large number of
polar alcohol groups, the lower carbohydrates are mostly water
49
soluble. As the molecular weight increases, water insolubility
can arise. Carbohydrates are often difficult to crystallize.
The tests described below will give information about the
class of carbohydrate to which the test substance belongs.
Perform the tests as described below and draw conclusions about
the unknowns that were assigned. It is possible that you may
not be able to fully identify a given unknown but clearly state
the conclusions that can be made.
EXPERIMENTAL PROCEDURE:
Perform the following identification tests on each of the
six sugars to be tested: glucose, fructose, xylose, sucrose,
lactose, and maltose. For your classification tests, you will
be using 1 % solutions of each of the sugars.
1) Red Tetrazolium Test
This test distinguishes between reducing and nonreducing sugars. In clearly labeled test tubes, place one drop
of the sugar to be tested, and add the red tetrazolium solution
(1 mL) and 3 M sodium hydroxide solution (1 drop). Put the tube
in a hot water bath and estimate the time that it takes for a
color to appear.
2) Barfoed’s Test
This test distinguishes between mono and disaccharides
that are reducing sugars. In clearly labeled test tubes, place
the sugar to be tested (1 mL) and add the Barfoed’s reagent (0.5
mL). Put the tube in a hot water bath and estimate the time
that it takes for a red precipitate to form.
3) Bial’s Test
This test distinguishes between pentoses and hexoses.
In clearly labeled test tubes, place the sugar to be tested (1
mL), add the Bial’s reagent (1 mL) and a boiling chip. Heat the
tubes in a sand bath and estimate the time that it takes for a
color to form. Also note the intensity of the color that
develops. As a standard of reference, add the Bial’s reagent (1
mL) to water (1 ml) and heat that along with your samples for
comparison.
4) Seliwanov’s Test
This test distinguishes between aldohexoses and
ketohexoses. Place Seliwanov’s reagent (1 ml) in each clearly
labeled test tubes. Add the sugar to be tested (5 drops),
agitate to mix, then heat in a water bath for 5 minutes. Note
the color and its intensity.
IMPORTANT INFORMATION ABOUT THE REPORT:
You will be assigned a number of unknowns to determine
using the tests described above. For your report, be sure to
50
identify by unknown number and class name for each unknown, if
possible. After you give this information, be sure to carefully
and completely describe how you reached your decision. Tell the
tests you did to determine what the compound was and how you
eliminated other possibilities.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
LAB 12:
HYDROLYSIS OF METHYL BENZOATE
PURPOSE:
This experiment will use microwave energy to cause a
hydrolysis of the ester methyl benzoate to benzoic acid using a
5% aqueous sodium hydroxide solution. After the reaction
mixture cools, the solution will need to be acidified to cause
the precipitation of benzoic acid. This experiment will also
51
introduce the concept of Green Metrics.
(Green Metrics).
Please read Appendix F
IMPORTANT REACTIONS:
O
O
C
OCH3
1) 5 % NaOH
C
OH
2) conc. HCl
Methyl Benzoate
M. Mass 136.16
bp 198-199oC
Benzoic Acid
M. Mass 122.12
mp 121-123 oC
BACKGROUND INFORMATION:
The hydrolysis of an ester is an easy and important
reaction in organic chemistry. One can use an acid or a base to
shorten the time needed for the reaction to occur.
The acid catalyzed hydrolysis of an ester gives the product
in the free acid form without further pH adjustment. While this
may seem preferable, it is seldom done as this reaction is
reversible and the equilibrium process significantly lowers the
yield.
The base promoted reaction forms the sodium salt of the
carboxylic acid which cannot enter into an equilibrium reaction
so the reaction can proceed to completion giving a high yield of
product. Note that the base, sodium hydroxide, is not a
catalyst in this reaction as it is consumed in forming the
sodium salt. The free acid form is recovered from the sodium
salt quite easily by a simple pH adjustment. In this reaction,
concentrated hydrochloric acid will be used to acidify the basic
reaction product. Since benzoic acid is moderately water
soluble, it is necessary to limit the amount of water in the
solution.
Microwave heating will be used in this experiment. As
mentioned in an earlier experiment, the use of microwave energy
for heating dates back to the 1960’s and became widespread in
the 1980’s. Since microwave energy can penetrate deep within a
molecule, the entire molecule can be heated at the same time.
Conventional heating is generally done by conduction and heats
from the outside to the inside of the sample. Therefore,
microwave heating can be faster than conventional heating.
However, for heating to occur, the microwave energy needs to be
absorbed by the bonds in the molecule. Absorption of energy is
52
better in polar bonds and poor in nonpolar bonds. Hence, water
heats rapidly in a microwave oven. It is said that alkanes do
not heat well with microwave energy.
The design of a microwave oven presents some challenges to
the designer. It is hard to have a uniform distribution of
microwave energy in the cabinet. Further, if no absorption of
microwave energy occurs a reflection of energy in the unit can
destroy to apparatus. Some manufacturers warn that operating a
microwave oven when empty can ruin the oven.
Microwave ovens can also cause fires. Many people who have
made popcorn in a microwave oven have seen burnt popcorn kernels
at one time or another. It is important to remember that three
things are needed for a fire to start: a source of ignition such
as microwave energy, a combustible substance such as many
organic compounds, and a source of oxygen such as air. It is
important that one follows the experimental details carefully to
work in a safe manner.
Microwave energy can penetrate the human body and can
interfere with certain electronic devices that may be implanted
for health reasons (such a cardiac pacemakers). If you have
implanted electronic devices, let the Instructor know and avoid
the lab while the microwave unit is turned on.
Please make careful observations during this experiment and
comment on any success or failure in your report.
EXPERIMENTAL PROCEDURE:
You will use the laboratory microwave in this experiment.
Be especially careful when handling the microwave reaction tubes
as they are delicate and expensive to replace.
Place methyl benzoate (1.00 ml) in a microwave reaction
tube and add 5 % aqueous sodium hydroxide (10 ml). Add a
magnetic stirrer bar, then screw on the cap and place your tube
in the microwave turntable. Record the position number of your
reaction tube on the turntable. When all of the tubes have been
added, your instructor will place the turntable into the
microwave unit, close the door and select the correct filesetting for your reaction (Ester.rot). The program will take 12
minutes to run, followed by a 5 min. vent and cool down program.
On completion, your instructor will open the microwave door and
remove the turntable. Carefully remove your reaction tube, and
empty the contents into a beaker. Cool the contents to room
temperature, and acidify the solution with about 2 ml of
concentrated HCl. As acidification proceeds, solid benzoic acid
will precipitate. Be sure to check that the final solution is
acidic by using pH paper. Cool the mixture in an ice bath and
suction filter the benzoic acid. After the benzoic acid has
53
dried sufficiently, weigh the solid, take its melting point and
calculate the percent yield.
IMPORTANT INFORMATION ABOUT THE REPORT:
The report for this experiment will follow the usual format
for synthesis reactions. Be sure the percent yield calculation
is carefully done. Also, record the melting point range of the
final product and compare that melting point to the reported
melting point of benzoic acid. Using these data, discuss the
relative success of the experiment. Also, be sure to critique
the effectiveness of using microwave heating to cause the
reaction to occur.
END OF EXPERIMENT.
© 2009 STEPHEN ANDERSON AND ROBERT SHINE
APPENDIX A:
QUALITATIVE ORGANIC ANALYSIS
QUALITATIVE ORGANIC ANALYSIS
SIM-ORG PROGRAM HELP SECTION
LONG VERSION
Dr. Scott Frees and Dr. Robert Shine
Ramapo College of New Jersey
Mahwah, NJ 07430
CONTENTS:
Introduction
Strategy for Identifying and Unknown
54
Solubility Classification
Functional Group Classification Tests
Derivative Formation and Use
Final Identification of an Unknown Substance
This simulation program includes:
12 organic chemistry functional groups
24 classification tests
21 derivative tests
500 unknowns
GENERAL INTRODUCTION TO QUALITATIVE ORGANIC ANALYSIS
There are two methods for identifying the structure of an
unknown organic compound. The first and older method is to run
classification tests to identify the functional group of the
compound followed by the production of one or more derivative
compounds to confirm the exact nature of the unknown. The
second method is to determine the spectral properties of the
unknown using mainly infrared and proton magnetic resonance
spectroscopy. The first method will be covered in this
simulation program. This program has 12 different functional
group classes and 500 different unknowns. It is planned that
the second method will be covered in a later revision of this
program.
The general method to determine the identity of an unknown
substance by classical methods is to gather some introductory
information about the compound. Note the odor, color, and
melting or boiling point of the material. Then find its
solubility characteristics by doing a solubility classification
as described below. From the information obtained from the
solubility classification run appropriate functional group tests
to identify the group to which the unknown belongs. Then the
unknown is converted into one or more different solids called
derivatives. Consulting tables of derivative melting points one
can then identify the exact identity of the unknown compound.
In order to intelligently conduct the functional group
classification tests a solubility classification is usually done
first to narrow down the possible functional group
possibilities.
A problem may arise when an unknown substance has two or
more functional groups in the molecule. This may lead to
confusion when interpreting the functional group and could lead
one to the wrong table of derivatives. Such unknowns are more
difficult to identify. There are a few such compounds in this
simulation program.
STRATEGY FOR IDENTIFYING AN UNKNOWN
55
The following steps should be taken to identify an unknown
compound:
1. Perform a solubility classification test to determine the
possible functional group classes to which the unknown may
belong.
2. Narrow the choices of possible functional groups to one
group by performing appropriate functional group tests.
3. Make one or more derivatives to finally determine the exact
identity of the unknown.
The above approach should lead to a successful identification of
an unknown about 80 % of the time. In other cases, the unknown
may pose difficulties that would require imagination and careful
analysis of the data to be successful in its identification.
SOLUBILITY TEST ANALYSIS:
Obtain the solubility class for the assigned unknown.
Shown below is a list of possible functional groups for each
solubility class. This classification method is not exact and
may need further thought and imagination in certain cases.
These solubility classes and their consequences can be
summarized below:
S1
These are very polar compounds which consist of salts of
carboxylic acids or amines. It is also possible the compound is
of low molecular weight and has many polar functional groups
such as a carbohydrate.
S2
These compounds are low molecular weight (generally less
than 5 carbons) with a polar functional group such as carboxylic
acid, amine, alcohol, aldehyde, or ketone.
A1
Higher molecular weight carboxylic acids fall into this
class.
A2
Phenols show this kind of solubility.
B1
Primary, secondary and tertiary amines fall into this
class. However, if there are two or more phenyl groups on the
nitrogen, the amine will probably not be basic enough to form
the salt and will, then, be insoluble.
N1
These are higher molecular weight compounds (generally more
than 9 carbons) containing an oxygen atom.
N2
These are medium size molecules (generally containing from
5 to 9 carbons) containing an oxygen atom.
IN
These are neutral compounds. Alkyl halides and alkanes
fall into this class.
FUNCTIONAL GROUP ANALYSIS:
Below are listed 24 chemical tests that could be used to
help identify an unknown. The tests are listed in
numerical/alphabetical order.
23. Introduction to qualitative tests
56
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
47.
2,4-dinitrophenylhydrazone
Acetyl chloride
Basic hydrolysis
Beilstein
Benedict
Bromine in carbon tetrachloride
Ceric nitrate
Chromic acid
Combustion
Ferric chloride
Ferric hydroxamate
Ferrous hydroxide
Hinsberg
Hydroxylamine hydrochloride
Iodoform
Lucas
Nitrous acid
pH in ethanol/water
Potassium permanganate
Silver nitrate in ethanol
Sodium fusion
Sodium iodide in acetone
Solubility
Tollens
DERIVATIVE USAGE:
Below are listed 21 derivatives that could be prepared from
various unknowns to help in a final determination of the
unknown. The derivatives are listed in numerical/alphabetical
order.
22.
Introduction to derivative use
23.
1-naphthylurethane
24.
2,4-dinitrophenylhydrazone
25.
3,5-dinitrobenzoate
26.
Acetamide
27.
Acid from hydrolysis
28.
Amide
29.
Anilide
30.
Benzamide
31. Benzenesulfonamide
32. Bromo derivative
33. Methiodide
34. Neutralization equivalent
35. Oxime
36. Phenylhydrazone
37. Phenylurethan
57
38.
39.
40.
41.
42.
43.
Picrate
p-Nitrobenzyl ester
p-Nitrophenylhydrazone
p-Toluenesulfonamide
p-Toluidide
Semicarbazone
SOLUBILITY CLASSIFICATION
The solubility of an organic compound in various solvents
can give valuable information about the unknown. The general
rule of 'like dissolves like' or 'polar compounds dissolve more
readily in polar solvents' is useful. Also, organic acids (such
as carboxylic acids and phenols) react with bases to form water
soluble salts and organic bases (such as amines) react with
acids to form water soluble salts. It should be noted that the
polarity of an organic compound is increased by the kind and
number of polar functional groups in the molecule and that the
polarity decreases as the size of the non polar aliphatic group
in the molecule increases.
With this background, one begins the solubility
classification by adding 3 drops or 3 mg of the unknown to 3 ml
of water and shaking the mixture. If the unknown dissolves, it
is a polar compound and in placed in solubility group S1. An
unknown in class S1 is then tested as above using ether as the
solvent. If it dissolved in both water and ether it is then
placed in class S2. For unknowns that do not fall into either
class S1 or S2, the unknown’s solubility in 5% sodium
bicarbonate is determined. If it is soluble, the unknown is
placed in class A1. If it is not soluble, the solubility in 5%
sodium hydroxide is studied. If it is soluble at this point,
the unknown belongs in class A2. If an unknown is insoluble to
this point it is next tested for solubility in 5% hydrochloric
acid. Compounds soluble in 5% hydrochloric acid are placed in
solubility class B1. For compounds insoluble to this point the
next solvent to try is concentrated sulfuric acid. Unknowns
soluble in only this acid are placed in solubility class N1.
A
further distinction can be made for compounds soluble in
concentrated sulfuric acid by testing their solubility in 85%
phosphoric acid. Such compounds that are soluble in 85%
phosphoric acid are placed in class N2. Finally, compounds
insoluble to this point are placed in class IN.
These solubility classes and their consequences can be
summarized below:
S1
These are very polar compounds which consist of salts of
carboxylic acids or amines. It is also possible the compound is
of low molecular weight and has many polar functional groups
such as a carbohydrate.
58
S2
These compounds are low molecular weight (generally less
than 5 carbons) with a polar functional group such as carboxylic
acid, amine, alcohol, aldehyde, or ketone.
A1
Higher molecular weight carboxylic acids fall into this
class.
A2
Phenols show this kind of solubility.
B1
Primary, secondary and tertiary amines fall into this
class. However, if there are two or more phenyl groups on the
nitrogen, the amine will probably not be basic enough to form
the salt and will, then, be insoluble.
N1
These are higher molecular weight compounds (generally more
than 9 carbons) containing an oxygen atom.
N2
These are medium size molecules (generally containing from
5 to 9 carbons) containing an oxygen atom.
IN
These are neutral compounds. Alkyl halides and alkanes
fall into this class.
The results of a solubility classification should not be
strictly interpreted as there are many overlaps. Use the
results of this classification only as a focus into which
classification tests should be done first.
FUNCTIONAL GROUP CLASSIFICATION TESTS
INTRODUCTION TO QUALITATIVE TESTS - The first test that
should be done is a solubility test to determine the class or
classes to which the unknown belongs. From the results of the
solubility tests, some idea of the type of organic compound
should be evident. If the solubility test results put the
unknown substance in the ‘Neutral’ section, it is recommended
that the classification tests be done in this order: aldehydes,
ketones, alcohols, esters, amides, nitriles, ethers, alkenes and
alkynes. Select a test from the list of tests that would help
confirm the presence or absence of the suspected functional
group class. Do as many tests that may be necessary to
absolutely confirm the functional group to which the unknown
belongs. Be careful to interpret correctly the test results for
those unknowns that may contain two or more functional groups.
At that point, proceed to the preparation of derivatives to
identity the exact identity of the unknown.
2,4-DINITROPHENYLHYDRAZINE TEST (for aldehydes and ketones) This test will be positive for an aldehyde or ketone as
indicated by the formation of a yellow, orange or red
precipitate which is called a 2,4-dinitrophenylhydrazone. This
precipitate can also be used as a derivative for the unknown if
its melting point is determined (see below for derivative use).
The color of the precipitate can help further identify the
59
extent of conjugation for the carbonyl group. Highly conjugated
aromatic aldehydes or ketones generally give red solids whereas
non conjugated carbonyl compounds give yellow products.
ACETYL CHLORIDE (for acidic hydrogen compounds) - This test will
help identify carboxylic acids, phenols and alcohols. A
positive test will be noted by the evolution of heat which may
be hard to detect. So, this test may give false positive or
negative tests depending on the expertise of the person doing
the test. In some cases, a solid (usually white) may form. If
this happens, the solid, if isolated and its melting point is
determined, could be used as a derivative for the unknown. If
water is present in the unknown, the test will probably give a
false positive test as acetyl chloride reacts vigorously with
water.
BASIC HYDROLYSIS (for amides, esters and nitriles) - Amides and
esters can be hydrolyzed by heating in a sodium hydroxide
solution. This reaction pH gives the acid as a water soluble
carboxylate salt. Acidifying this solution with concentrated
hydrochloric acid would result in a precipitate if the
carboxylic acid is water insoluble. If this precipitate is
formed, it should be filtered and used as a derivative for the
unknown.
BEILSTEIN TEST (for halogenated compounds) - Placing a small
amount of an organic compound on the end of a copper wire and
heating it in the open flame of a Bunsen burner results in a
transient green color in the flame if the compound contains a
halogen atom. If the unknown is volatile, it may evaporate
before it burns resulting in a negative test.
BENEDICT TEST (for aldehydes and sugars) - When easily oxidized
organic compound (such as aldehydes and reducing sugars) is
heated in Benedict’s solution (which is a blue solution
containing a complexed copper (II) ion) a brick red precipitate
of cuprous oxide forms. If the unknown is not soluble in the
reagent a negative test may be observed due to the lack of a
reaction.
BROMINE IN CARBON TETRACHLORIDE (for alkenes and alkynes) - When
a solution bromine in carbon tetrachloride is added drop wise to
an colorless unknown compound, the brownish color of elemental
bromine disappears as the bromine adds to the unsaturated
organic compound.
60
CERIC NITRATE (for alcohols and phenols) - Alcohols with 10
carbons or less will give a red color with ceric nitrate
solution whereas phenols will give a green-brown to brown
precipitate. Easily oxidized compounds may destroy the ceric
nitrate solution before the test results may be observed.
CHROMIC ACID (for aldehydes, primary and secondary alcohols) Easily oxidized compounds convert the red chromium (VI) ion to a
green chromium (III) precipitate.
COMBUSTION (for flammable or combustible organic compounds) When a few milligrams of an organic liquid or solid are placed
directly into a Bunsen burner flame they often burn. Note that
highly halogenated organic compounds may not burn. Very
volatile compounds may evaporate before burning or burn very
rapidly. The manner in which a compound burns can give some
information about its nature. Highly oxygenated compounds burn
with a blue flame, aliphatic compounds give a yellow flame and
aromatic compounds give a sooty flame.
FERRIC CHLORIDE (for phenols) - Some (but not all) phenols give
a color when ferric chloride solution is added. This test is
not a definitive one and the results should be carefully
evaluated.
FERRIC HYDROXAMATE (for esters, acid chloride and anhydrides) Esters of carboxylic acids give a magenta color with this
reagent. Acid chloride and anhydrides give a magenta or
burgundy color with the test reagent.
FERROUS HYDROXIDE (for nitro compounds) - Most compounds that
contain a nitro group will give a brown to red-brown precipitate
of ferric hydroxide by oxidation of ferrous hydroxide.
HINSBERG TEST (to distinguish primary, secondary and tertiary
amines) - Benzenesulfonyl chloride can be used to distinguish
primary, secondary and tertiary amines. The amine functional
group must be confirmed before this test can be performed as the
test will give very confusing results with any other functional
group. Primary amines give a solid benzenesulfonamide product
that is soluble in 5% sodium hydroxide. Secondary amines give a
solid benzenesulfonamide product that is insoluble in 5% sodium
hydroxide. Tertiary amines do not react with benzenesulfonyl
chloride.
HYDROXYLAMINE HYDROCHLORIDE (for aldehydes and ketones) Aldehydes and most ketones give a red color when added to a
61
solution of hydroxylamine hydrochloride in ethanol-water that
has a universal indicator added.
IODOFORM TEST (for methyl carbonyl compounds) - This test is
mainly used to identify methyl ketones. The iodoform regent
iodinates the methyl group which then cleaves in the basic
solution. One should confirm the presence of a carbonyl group
in the unknown before this test is done as misleading results
could occur with other compounds. For example, acetaldehyde and
alcohols that have a methyl group bonded to the C-OH group can
also give a positive test since such an alcohol can be oxidized
to a methyl ketone by the iodoform reagent.
LUCAS TEST (to distinguish primary, secondary and tertiary
alcohols of six carbons or less) - A solution of zinc chloride
in aqueous hydrochloric acid can be used to distinguish primary,
secondary and tertiary alcohols. The unknown compound must be
soluble in the reagent in order for the test to be valid. When
a tertiary alcohol is added drop wise to the reagent, an
immediate second layer of a liquid alkyl chloride is formed.
Secondary alcohols form a second layer of the insoluble alkyl
chloride in three to 5 minutes. Primary alcohols are unreactive
with the Lucas reagent.
NITROUS ACID (to distinguish primary, secondary and tertiary
amines) - Primary aromatic amines give nitrogen gas evolution
with the nitrous acid reagent. Other aromatic amines can
undergo coupling reactions to form colored products.
pH IN ETHANOL (to distinguish low molecular weight acidic or
basic compounds) - The pH of compounds that are soluble in water
or aqueous alcohol can be measured. If the pH is in the acid
range the compound can be a carboxylic acid, acid chloride or
anhydride. If the pH is in the basic range, the compound may be
an amine. Organic salts may hydrolyze in water which can lead
to acidic or basic solutions.
POTASSIUM PERMANGANATE (for compounds that can be oxidized) Organic compounds that can be readily oxidized will convert the
purple permanganate ion to a brown precipitate of manganese
dioxide. Such organic compounds include: aldehydes, reducing
sugars, primary or secondary alcohols and some alkenes and
alkynes.
SILVER NITRATE IN ETHANOL (for alkyl halides that can undergo
Sn1 reactions) - Tertiary alkyl halides will give a white to
yellow silver halide precipitate with this reagent. Some
62
secondary halides will react more slowly.
halides do not react.
Aryl and vinyl
SODIUM FUSION (for compounds that contain halogen, nitrogen or
sulfur) - When an organic compound is placed in molten elemental
sodium the molecules are violently destroyed. Any halogen,
nitrogen or sulfur in the original molecule is converted to
ionic materials which are then identified. The halide is
identified by precipitation with silver ions. The sulfide ion
is identified by precipitation with lead ions. The cyanide ion
formed from the nitrogen in the molecule is converted into
Prussian blue by ferrous sulfate.
SODIUM IODIDE IN ACETONE (for alkyl halides that can undergo Sn2
reactions) - Primary and some secondary alkyl chlorides or
bromides will give a precipitate of sodium iodide in the
reagent. Alkyl iodides will not give a precipitate. Aryl or
vinyl halides do not react.
SOLUBILITY (for general classification of organic compounds) See
SOLUBILITY CLASSIFICATION section above.
TOLLENS TEST (for aldehydes and reducing sugars) - Water soluble
aldehydes and reducing sugars give a silver mirror or black
precipitate of elemental silver with the Tollens reagent.
DERIVATIVE FORMATION AND USE
INTRODUCTION TO DERIVATIVE USE - Derivative Tests - Once
the classification tests have indicated an organic family of
compounds (e.g. an aldehyde), one can see if derivatives of the
unknown can be synthesized to help in its identification. Based
on the results of the classification tests, the correct
derivative tests to use can be determined. On selecting the
relevant test, the results will be illustrated. If the
derivative test is positive, it is evidence that the correct
family of compound has been chosen, and the melting point of the
derivative should be recorded on a data sheet. Order all the
derivative tests relevant to the search (e.g. for an aldehyde,
obtain the melting points of both the semicarbazone and 2,4dinitrophenylhydrazine derivatives) and then proceed to the
final identification of the unknown substance.
1-NAPHTHYLURETHANE DERIVATIVE - (for alcohols and phenols)
2,4-DINITROPHENYLHYDRAZONE - (for aldehydes and ketones)
3,5-DINITROBENZOATE - (for alcohols)
63
ACETAMIDE - (for primary and secondary amines)
ACID FROM HYDROLYSIS - (for acid chloride, anhydride, ester,
amides, and nitriles)
AMIDE - (for carboxylic acids, acid chlorides, and anhydrides)
ANILIDE - (for carboxylic acids, acid chlorides, and anhydrides)
BENZAMIDE - (for primary and secondary amines)
BENZENESULFONAMIDE - (for primary and secondary amines)
BROMO DERIVATIVE - (for phenols)
METHIODIDE - (for tertiary amines)
NEUTRALIZATION EQUIVALENT - (for acids, amides, esters and
nitriles)
OXIME - (for aldehydes and ketones)
PHENYLHYDRAZONE - (for aldehydes and ketones)
PHENYLURETHAN - (for alcohols and amines)
PICRATE - (for tertiary amines)
p-NITROBENZYL ESTER - (for carboxylic acids)
p-NITROPHENYLHYDRAZONE - (for aldehydes and ketones)
p-TOLUENESULFONAMIDE - (for primary and secondary amines)
p-TOLUIDIDE - (for primary and secondary amines)
SEMICARBAZONE - (for aldehydes and ketones)
FINAL IDENTIFICATION OF AN UNKNOWN SUBSTANCE
Tables of organic substances can be used to identify the
unknown based on the results of the classification tests and the
derivative melting point results.
TABLES OF UNKNOWNS - Once the derivative melting point data have
been recorded, enter the Tables of Unknowns by selecting the
suspected functional group class. Here a list of organic
64
compounds separated by type will appear. Select the family to
which the unknown belongs. A list of all the compounds of that
type, presented in order of increasing boiling/melting point
will appear. Also listed are the melting points of any
derivatives that can be synthesized from the class of the
unknown compound. By matching the table data with the unknown
compound data obtained above, one can identify the unknown.
ANSWER TRIAL - Based on all the melting point data in the Tables
of Unknowns, one will now have an idea of what the unknown
sample is. To see if you are correct, you can enter it into the
program by selecting Answer Trial. Make sure that you select the
compound correctly, exactly as it appears in the table of
unknowns. If you are correct, a congratulation message will
appear. If you are wrong, first re-check your data for the
unknown. If it is still incorrect, then you will need to go back
into the program in order to correctly identify the unknown
sample.
© 2009 Scott Frees and Robert Shine
65
APPENDIX B:
SAFETY ISSUES
INTRODUCTION:
A very important aspect of laboratory work is working
safely. It is your responsibility to yourself and the other
people in the laboratory to work in a serious and careful
manner. If you are not sure about the dangers involved in what
you are assigned to do, be sure to ask the Instructor before you
begin. You should consult the material safety data sheets
(msds) for those chemicals you will be working with before
coming to the lab. You can find msds data by typing the
chemical name followed by msds in a Google search box. For
example msds data for acetone could be found by typing acetone
msds in the search box.
If you have allergies, you should consult your Allergist
for advice in working with organic chemicals. If you are
pregnant or become pregnant, you should consult your doctor for
advice in working with organic chemicals.
There are risks involved with all activities you do. By
knowing what those risks are and taking prudent actions, you can
lessen the dangers you face and thereby lead a relatively safe
life. The dangers you are likely to face in the organic
chemistry laboratory are due to:
1. Equipment.
2. Toxic chemicals
3. Flammable chemicals
EQUIPMENT:
You will use glassware, plastic ware, and electrical
heating equipment in the lab. As you know, glass items can
break and cause cuts that can be minor or severe. You should
exercise care when handling glassware to minimize breakage. If
a glass item breaks, notify the Instructor who will then use a
broom and dustpan to clean up the area. Broken or discarded
glassware must be placed in the separate container that is
marked for broken glass. No other items other than glassware
should be placed in that container.
66
Plastic ware generally has no safety concerns and is safe
to use.
Heating in the lab will generally be done using electrical
heating equipment such as hot plates and heating mantles. We
will not use Bunsen burners in the laboratory. We may use steam
baths on occasion. Steam can cause a bad scalding burn.
Hotplates and heating mantles do not change appearance when they
are hot so you should always assume they are hot until proven
otherwise. There can also be an electrical shock hazard with
any electrical equipment. Electrical outlets in the organic
chemistry laboratory are protected by ground fault interrupter
circuit breakers.
Also be aware that heating equipment can be hot enough to
exceed the flash point of a chemical and can start a fire.
Chemicals that have a low flash point can be ignited by a warm
hot plate. Evaporating diethyl ether from a beaker on a
hotplate caused a fire in our organic chemistry laboratory many
years ago.
TOXIC CHEMICALS:
Eye protection must be worn in the laboratory whenever
anyone in the lab is working with chemicals. Only department
approved eye goggles can be used. If, at any time, you suspect
that a chemical got onto your skin or eyes, immediately wash the
affected area with plenty of cold water for a significant period
of time. Be sure to notify the Instructor after you begin the
washing process. Chemicals that are immediately washed from the
skin will cause less damage than those that are allowed to
remain on the skin until you feel pain. So, even if you feel no
pain, wash the affected area immediately.
Many chemicals have toxic properties which vary from
compound to compound. The best source of information about the
toxic properties of chemicals you will use is the material
safety data sheet (msds) for that chemical. Be aware that
chemicals can enter the body by inhalation, ingestion,
absorption or injection through the skin. You should use gloves
to protect the skin and should rinse your hands after handling
chemicals. When you leave the lab you should thoroughly wash
your hands.
Ingestion of chemicals can be avoided by not putting
anything in your mouth during the laboratory period. Never
pipette by mouth; use approved suctioning devices. Never eat or
drink any food in the lab, including chewing gum, as it could
have been contaminated.
Inhalation of volatile chemicals can be avoided by working
in the fume hood. Try to minimize the time a volatile chemical
67
will be exposed to the air outside the hood. Weigh such
substances quickly and move them immediately to the hood.
Some chemicals used in the lab are corrosive. Generally
these include acids and bases. The more concentrated the acid
or base, the more corrosive it will be. So use extreme care
with concentrated sulfuric acid, hydrochloric acid, nitric acid,
phosphoric acid, and sodium hydroxide solutions. Nitric acid
will cause orange patches to appear on the affected skin in one
to three days. This orange patch will slowly wear off. Silver
nitrate will cause black stains to appear in the affected area
within a few hours after exposure and will wear off in a few
days. Volatile organic solvents that enter the body can cause
systemic poisoning. Often, the liver or kidneys are affected.
Be sure to read the material safety data sheet for specific
information about the chemicals with which you are working.
FLAMMABLE CHEMICALS:
Many organic chemicals can burn. Halogenated organic
compounds are usually less flammable than others but they tend
to be more toxic, especially to the liver. Compounds with a
high percentage of carbon (such as aromatic hydrocarbons) burn
with a very black sooty flame. Other hydrocarbons burn with a
yellow flame and as the oxygen content of the compound
increases, the flame becomes more bluish.
In order to have a fire start, three things are needed.
You must have a compound that can burn, an oxidizing material
such as air, and an ignition source that will raise the
temperature of the flammable substance above its flash point.
Of real concern is whether or not a compound can cause a
fire. There are terms whose meaning you need to know. These
terms are: nonflammable, inflammable, flammable, and
combustible. Nonflammable means the compound will not burn
under reasonable conditions. They pose no fire hazard. Water
is such a substance. Inflammable is a very bad choice for a
word. The dictionary defines inflammable as "capable of being
set on fire; combustible." Inflammable does not mean "not
flammable." The word inflammable should not be used. A
flammable substance is "one that is easily set on fire" and a
combustible substance is "capable of being set on fire."
Flammable substances, with their lower flash points, pose a more
serious fire hazard than combustible substances. Gasoline would
be considered flammable and wood would be considered
combustible. So, use care when working with flammable and
combustible substances, especially with flammable substances.
© 2009 Stephen Anderson and Robert Shine
68
APPENDIX C:
COMMENTS ABOUT WRITING STYLE
Before you begin writing lab reports for this course, you
should carefully study the following statements which are
presented to help you achieve good grades. Failure to use this
advice could result in a lower lab grade.
1. On all written work you submit, place your name, the full
descriptive name of the experiment, and the day of the week
(that is, Monday, Tuesday, Wednesday, or Thursday) that you have
lab.
2. Reports are due at the beginning of the next class meeting.
If you computer dies, submit the report on time, neatly
handwritten. Reports cannot be submitted electronically unless
allowed by your Instructor.
3. Use correct grammar and spelling. Use adjectives, nouns and
verbs correctly. Use scientific terms correctly. Proofread your
report and check all spelling as spell checkers do not recognize
the misuse of words (such as to, too and two).
4. Use terms (especially scientific terms) correctly. Do not
misspell the name of a chemical. Failure to use technical terms
correctly will have a definite negative impact on your report
grade. For example, do not report the boiling point of a solid;
report its melting point.
5. Do not be vague or overly explicit. Give only the important
data, observations and conclusions.
6. Your report should have a correct, logical flow. For
example, give the data before the conclusions that are made.
7. When giving a measurement, be sure to include both the number
(with the correct number of significant figures) and correct
units.
8. Pay attention to the correct use of significant figures. See
Appendix D for more information about the correct use of
significant figures.
9. Do not start a sentence with a digit. Spell out any numbers
that start a sentence.
10. Use the third person, passive voice in science report
writing.
11. The data page that you submit when you leave the lab is part
of your lab grade. The data page must be clearly presented, as
neat as possible, and must give all the critical measurements
(numbers and units) you made in the lab. Computations of
results may be left until the final report is written if they
are difficult to do. Simple computations may be included with
the data sheet.
12. Be sure that each section in the report has an introductory
sentence.
69
13. Cite all references used and be exact in giving each
reference.
14. The introduction section must have structures of important
compounds or a chemical equation drawn early in the section.
15. The introduction section should deal with the theory of the
experiment and not give experimental details.
16. The experimental section can be brief with a reference to
the lab manual. You need add only the changes you made that
differed from the lab manual.
17. As much as possible, tabulate data and place them near the
text that describe it. Be sure the table has a meaningful title
and that the data are presented in a clear manner.
18. Do not describe a math formula in text. Draw the formula
and separate it from the text by at least one line.
19. For results that are computed from lab data, be sure to show
how the computation was done. That is, show the math used.
When doing computations in the lab report, show the general
formula and then show the formula with your actual data to show
how you obtained your result. Set the mathematics away from
text so it stands out.
20. Fully explain the data. Do not leave any critical data out
of the report. If you calculated the amount of a substance by
measuring the weight of a container empty and then again with
the sample in it, both weights must be in the report along with
the final weight.
21. Be sure data, calculations and conclusions are tied
together. If these items are in different parts of the report,
be sure to tell the reader where they can be found.
22. All data in the lab report should be able to be traced back
to the experimental data you recorded on the data sheet you
submitted. Do not take any shortcuts in data handling. You
must show all relationships in a logical, orderly manner, and
you must show how results were calculated.
23. When giving melting point or boiling point data, be sure to
report these data as a range, and be sure to give the accepted
literature values in parentheses immediately after your
experimental data.
24. The conclusion section may be brief but should tell what the
objectives of the experiment were and if they were achieved.
25. Do not report a percent error unless told to do so. We
measure percent recovery or percent yield. Be sure you know the
difference between these terms.
26. Repeating errors, such as the misspelling of a chemical,
will be noted only once when reports are graded.
27. Do not capitalize a chemical name unless it is the first
word in the sentence.
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28. Mass is not used as a verb in this course. A chemical can
be weighed but not massed. Also, precipitates are filtered, not
funneled.
29. Two words are often misused in this course. The first is
'separate' which is often misspelled with an 'e' after the 'p'.
Fortunately, spell checkers fix this error. The other misused
word is 'vial' which many students write as 'vile'. A spell
checker does not repair this mistake. The dictionary defines
'vile' as: "mean, worthless, unclean, repulsive, bad." The same
dictionary defines the homonym 'vial' as: "a small vessel." Be
sure to use these two terms correctly.
30. Do not use the first or second person in scientific writing.
Do not use I, we, or you.
31. A rewrite of a previously graded lab report will not be
accepted unless it was authorized and agreed upon by the
Instructor before it was done.
32. More information about good report writing style for
chemists can be found on the Web by doing a Google search on
‘writing style for chemists’.
© 2009 Stephen Anderson and Robert Shine
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APPENDIX D:
MEASUREMENTS AND SIGNIFICANT FIGURES
INTRODUCTION:
A very important aspect of laboratory work is making and
reporting measurements carefully. A significant part of your
grade will be based on how you gather and report data. You will
need to know which measurements will need to be made carefully
and which are less important and can be made quickly with less
accuracy.
There are three terms that you will need to know and
understand: precision, accuracy, and significant figures. These
terms have similar meaning and are often confused.
precision--The ability of repeated measurements to
have the same value. If you weigh an item three different
times, the number of grams should be exact or very close for all
the measurements.
accuracy--The agreement of a measurement with the
accepted value reported for that value. If you measure the
density of water at 4 degrees Celsius, it should be 1.00 g/ml.
significant figures--The number of digits that can be
reported for a measurement. If you weigh some item on the top
loading balance in our laboratory, it can be recorded to the
third decimal place if using units of grams, such as, 1.234 g.
In this laboratory course, the correct use of significant
figures will be the most important of the three. Accuracy will
be the next most important and precision will generally be
disregarded as you will usually not make repeated measurements
of the same data item.
SIGNIFICANT FIGURES:
The number of significant figures you give in your lab
report is governed by the limits of the measuring devices you
use and the care you exercise in making a measurement.
Mathematical manipulation of data can never increase the number
of significant figures in your result.
You will need to know what measurements are important and
which are not. Do not waste time in making a very careful
measurement on some less significant piece of data. For
example, the exact amount of a reagent is needed but the precise
volume of solvent in which it is dissolved is often not needed.
Be sure to record important data to the level of precision
the measuring instrument allows. If the directions tell you to
measure out exactly 0.500 g of a compound, then you will have to
spend some time to carefully get 0.500 g. However, often the
directions will say to measure about 0.500 g of a compound.
Here, you can quickly weigh out an amount that is approximately
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0.500 g but you must record your exact weight. For example, you
may have weighed 0.476 g. You would then use that figure (0.476
g) in your report and further calculations.
It is important that you know the difference between 0.05
and 0.050. The first of these (0.05) has one significant figure
while the second (0.050) has two significant figures. A zero
used to place the decimal point is not a significant figure.
So, if you carefully weighed out 0.500 g and wrote it as 0.5 g
or 0.50 g, you would be wrong. You must show all the
significant figures allowed by the measurement you made along
with the correct units such as grams (g), milligrams (mg),
milliliters (ml), etc.
In any measurement, the last significant figure has an
uncertainty associated with it. Often you will see the balance
going up and down over time in the last decimal place. So a
measurement such as 0.476 g really is 0.476 +/- 0.001 g.
In using conversion factors such as 1 pound/453.6 g, the
number 1 is exact and can be assumed to have the same number of
significant figures as the other value. So here, the conversion
factor is 1.000 pound/453.6 g. Also note that every conversion
factor equals one so the reciprocal also is true. That is,
453.6 g/1 pound is also true. In all your calculations, be sure
to show the numerical data and the correct units. Both are
required.
It is important to consider how to use significant figures
when doing mathematical operations. Using a calculator which
can report 8 digits does not make your result more accurate.
You must report your calculated result to the correct number of
significant figures allowed by the laboratory measurements and
not the calculator.
If the mathematical operation is addition or subtraction,
your result can only be reported to the decimal place of the
least accurate measurement. The following examples may clarify
this. If you add 123.4 g to .123 g, the result is 123.5 g. If
you add 1.2 g to .123 g, the result is 1.3 g. If you subtract
1.234 g from 1.236 g, the result is .002 g. Note that in
addition and especially subtraction, you can appear to lose
significant figures. So, in such cases, if one measurement can
only be made to the first decimal place, it is a waste of time
to make the other measurement carefully to the third decimal
place.
If the mathematical operation involves multiplication and
division, the result will have the number of significant figures
equal to that of the least significant piece of data. If you
multiply 123 by 12, the result is 1500 which has 2 significant
figures and 2 zeros to place the decimal point. Such results
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are better written in scientific notation (1.5 x 103) to avoid
confusion.
Be sure you fully understand the meaning and use of
significant figures as a major part of your laboratory grade
will be based on your lab measurements and data manipulation in
your lab reports.
© 2009 Stephen Anderson and Robert Shine
74
APPENDIX E:
PERCENT YIELD CALCULATION METHOD
The calculation of a per cent yield is a very important
part of those labs where a chemical synthesis has been done. In
your report be sure to correctly do the percent yield
calculation (showing the correct significant figures and units)
and present it in a very clear manner. Do not forget the show
the correct units with each measurement as you perform the
calculation. A percent yield calculation is an application of a
weight-weight problem which you learned in Fundamentals of
Chemistry.
You must show how the calculations are done in an area that
is separated from text. Do not put data details in paragraph
text. Present data details in tabular form and be sure this
data is near the text that makes reference to it for clarity of
presentation or, if the calculations have been attached to the
end of your report as an appendix, give a clear sentence that
refers the reader to this page. Calculations should be close to
where the final data are presented in your report. Briefly, a
percent yield calculation is an application of a weight-weight
problem in General Chemistry. You calculate the number of moles
(or millimoles) of each reagent. Determine which reagent is the
limiting reagent from the balanced equation. Catalysts are not
usually limiting reagents. Then, determine from the balanced
equation the maximum number of moles of the desired product that
could be obtained and this is your theoretical yield in moles.
Convert this number of moles of product to a theoretical weight
of product. Then, divide the weight of product that you
obtained by the theoretical weight of product you calculated and
multiply by 100 %. Alternatively, you could determine the
actual moles of product obtained by taking the mass of the
product isolated and dividing by its molecular weight. The
percent yield in that case would be the actual moles divided by
the theoretical moles times 100 %. Be sure to identify which
method you use by showing numerical and unit values for all data
in your calculations.
Percent yield calculations will be a
major part of your report grade in those labs where percent
yield data needs to be reported.
SAMPLE CALCULATION:
Below is just a guide to show you how the calculations are
done, presented in a manner to help you understand the process.
This is not an acceptable percent yield calculation for your lab
report. The method below was adapted from a reaction of a
diamine with an acid to give a salt which appeared in the
Organic Chemistry I laboratory manual.
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The balanced equation showed that 1 mole of diamine reacts with
1 mole of acid to give 1 mole of salt.
You started with 1.20 ml of diamine.
1.14 g of diamine
1.20 ml * .951 g/ml gives
1.14 g of diamine / 114 g/mole of diamine gives .0100 mole of
diamine used.
You also weighed some tartaric acid that varied from group to
group. Say your group weighed .732 g.
The number of moles of acid in the .732 g is .732 g / 150 g/mole
of tartaric acid or 0.00488 mole of tartaric acid.
From the balanced equation, the acid is the limiting reagent and
the theoretical yield of the product would be .00488 moles of
salt.
From the molecular weight of the product, the theoretical weight
of the product is 0.00488 mole * 264 g/mole of salt or 1.29 g.
If you obtained .847 g of product, your percent yield is
(.847 / 1.29 g) * 100% or 65.7 %.
© 2009 Stephen Anderson and Robert Shine
APPENDIX F:
GREEN METRICS
For most of this laboratory course, percent yield was used
to measure the efficiency of a synthetic reaction. However, the
percent yield does not consider the fate of other reagents,
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solvents or catalysts. It does not consider the costs involved
in handling byproducts and hazardous waste. As we have seen,
green chemistry focuses on finding methods for the development
of new, less polluting processes. Green metrics is a branch of
green chemistry which attempts to quantify the total
environmental cost of a process. Green metric calculations keep
track of the amount of material that goes into and comes out of
a chemical reaction. Common green metric terms include: percent
yield, E-factor, atom economy, atom efficiency, effective mass
yield and reaction mass efficiency. Each of these terms will be
described below.
The percent yield has been used throughout this course to
give a crude measure of the success of a synthetic reaction. It
is:
(actual yield/theoretical yield) * 100%
Percent yield could be increased by using
reaction conditions, minimizing competing
minimizing mechanical loss.
The E-factor (efficiency factor) is
correlates with the amount of organic and
in a chemical process. It is:
better processes or
reactions, and
a number that
aqueous waste produced
total waste in g/product weight in g
The smaller the E-factor, the better the process since less
waste is produced. The E-factor has a range of 0 to infinity.
Atom economy (or percent atom economy) is a theoretical
number that shows the amount of reactants that remain in the
final product. It is:
(MW of product/sum of MW of all reactants) * 100%
The bigger the number for atom economy, the higher the percent
of all reactants that remain in the final product. The range is
0% to 100%. Atom economy is dictated by the chemical reaction.
The Diels Alder reaction is an example of a reaction that has a
good atom economy.
Atom efficiency is a practical number that attempts to
join the concept of percent yield and atom economy. This metric
gives a good indication of the greenness on the process. Atom
efficiency is:
Percent yield * atom economy
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Atom efficiency has a range of 0% to 100% and the closer the
atom efficiency is to 100%, the greener the process.
Effective mass yield is the percentage of the mass of the
desired product relative to the mass of all hazardous materials
used in the synthesis. It is:
(product mass g/hazardous reagents mass g) * 100%
This metric evaluates the amount of hazardous reagents used in
making the final product. It may be difficult in determining
what is hazardous or not.
Reaction mass efficiency is the percentage of the mass of
reagents that remain in the final desired product. It takes
into account the stoichiometry, yield, and atom economy. It is:
(product mass in g/mass of reagents in g) * 100%
The larger the number for reaction mass efficiency, the better
the process. The range is 0% to 100%. Reaction mass efficiency
is similar to effective mass yield. The only difference is that
the effective mass yield takes into consideration the hazardous
reagents whereas the reaction mass efficiency uses the total
mass of all reagents.
It would be a worthwhile exercise for the student to apply
the above principles to an evaluation of the greenness of the
hydrolysis of methyl benzoate experiment or, indeed, any other
experiment performed this semester.
© 2009 Stephen Anderson and Robert Shine
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APPENDIX G:
CHEMICAL DATA
INTRODUCTION:
This appendix will present physical data and safety data
about chemical substances that are mentioned in the experiments
described in this manual. The data are presented in an Excel
spreadsheet format. Table 1 gives all the data in one location
but the printing is small and may be difficult to read. Table 2
gives safety information while Table 3 gives the physical
properties of the chemicals. Data were obtained from chemical
handbooks, supplier catalogs, and material safety data sheets.
In many cases, the value for a given piece of data such as a
melting point varied from source to source within a narrow
range. Therefore, you may find a data value from some source
you check that does not agree with what is reported in this
appendix. However, if you find any serious error in the data
tables, please send an e mail to Robert Shine
(bshine@ramapo.edu) informing him of the nature of the error. A
blank cell in the data tables indicate the value for that data
point was not found or does not apply. For example, the boiling
point of an inorganic solid is generally not useful in this
course.
Also, the density for a solid substance could be
meaningless for us.
Remember that you can obtain more complete information
from the Material Safety Data Sheet (msds) for a given
substance. You can obtain a material safety data sheet for a
compound by doing a Google search. For example, an msds for
acetone can be obtained by typing "acetone msds" (don't include
the quote marks) in the search box. Usually this search will
result in many hits so you can just link to one of the sources.
If you do not get any results from a Google search, try to
search using an alternate name for the chemical. With practice,
you will find your favorite source for an msds.
EXPLANATION OF COLUMN HEADINGS:
The ChemicalName column gives the usual name for the
substance listed. All tables are arranged alphabetically
according to the ChemicalName. The AlternateName column gives
another name for a given substance. The Formula column gives
the general chemical formula for that substance. If you compute
the molecular weight for that chemical formula, you would obtain
the data value in the Mol.Wt. column. The units for these data
are grams/mole. The next column, Melt.Pt., gives the melting
point in degrees Centigrade (Celsius). After this, comes the
column Boil.Pt. which gives the boiling point for the substance
in degrees Centigrade (Celsius). The Density column gives the
density for the substance is grams/ml. The density for a solid
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is not useful in this course but the density for a liquid could
give a useful method when measuring liquid reagents. One can
accurately measure a liquid by volume. The weight of that
sample would then be equal to the volume times the density. If
you know the weight you wish to measure, the volume would be
equal to the desired weight divided by the density. Expressed
in mathematical terms, the formulae are:
Volume = Weight / Density
Weight = Volume x Density
The remaining three columns give some safety data. The
CAS # is the Chemical Abstract Service number for the substance.
The CAS# is a unique identifier for a chemical assigned by the
American Chemical Society. The FlashPt gives the temperature at
which a substance can be readily ignited. Substances with a
flash point below 100 degrees Centigrade are classified as
flammable while those above 100 degrees are called combustible.
Be especially cautious with chemicals with a flash point below 0
degrees. The final column gives the NFPA Rating of the
substance. NFPA stands for the National Fire Protection
Association and their web site can be found at www.nfpa.org (not
.com) which is a 'for profit' organization. You can find more
information about this rating system by doing a Google search on
“nfpa diamond”. The rating assigns values from 0 to 4 for each
of three categories Health, Fire, and instability (which is
sometimes called reactive). A value of 0 indicates little or no
hazard whereas a value of 4 indicates an extreme hazard.
© 2009 Stephen Anderson and Robert Shine
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