Chemistry 121(001) Winter 2015
Introduction to Organic Chemistry and Biochemistry
Instructor Dr. Upali Siriwardane (Ph.D. Ohio State)
E-mail: upali@latech.edu
Office: 311 Carson Taylor Hall ; Phone: 318-257-4941;
Office Hours: MTW 8:00 - 10:00 am;
ThF 9:00 - 10:00 am 1:00 - 2:00 pm.
December 19, 2014: Test 1 (Chapters 12-13)
January 26 , 2015: Test 2 (Chapters 14-16)
February 13, 2015: Test 3 (Chapters 17-19)
March 2, 2015:
Test 4 (Chapters 20-22)
March 3 , 2015: Make Up Exam: Chapters 12-22)
Bring Scantron Sheet 882-E
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GHW Questions
GHW#3
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Chapter 12. Saturated Hydrocarbons
12.1 Organic and Inorganic Compounds, 341
12.2 Bonding Characteristics of the Carbon Atom, 342
12.3 Hydrocarbons and Hydrocarbon Derivatives, 342
12.4 Alkanes: Acyclic Saturated Hydrocarbons, 343
12.5 Structural Formulas, 344
12.6 Alkane Isomerism, 346
12.7 Conformations of Alkanes, 348
12.8 IUPAC Nomenclature for Alkanes, 350
12.9 Line-Angle Structural Formulas for Alkanes, 356
12.10 Classification of Carbon Atoms, 358
12.11 Branched-Chain Alkyl Groups, 359
12.12 Cycloalkanes, 361
12.13 IUPAC Nomenclature for Cycloalkanes, 362
12.14 Isomerism in Cycloalkanes, 363
12.15 Sources of Alkanes and Cycloalkanes, 365
12.16 Physical Properties of Alkanes and Cycloalkanes, 367
12.17 Chemical Properties of Alkanes and Cycloalkanes, 368
12.18 Halogenated Alkanes and Cycloalkanes, 371
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Chapter 13. Unsaturated Hydrocarbons
13.1 Unsaturated Hydrocarbons, 384
13.2 Characteristics of Alkenes and Cycloalkenes, 385
13.3 IUPAC Nomenclature for Alkenes and Cycloalkenes, 386
13.4 Line-Angle Structural Formulas for Alkenes, 389
13.5 Constitutional Isomerism in Alkenes, 390
13.6 Cis-Trans Isomerism in Alkenes, 391
13.7 Naturally Occurring Alkenes, 394
13.8 Physical Properties of Alkenes and Cycloalkenes, 396
13.9 Chemical Reactions of Alkenes, 396
13.10 Polymerization of Alkenes: Addition Polymers, 402
13.11 Alkynes, 406
13.12 Aromatic Hydrocarbons, 408
13.13 Names for Aromatic Hydrocarbons, 410
13.14 Aromatic Hydrocarbons: Physical Properties and Sources, 413
13.15 Chemical Reactions of Aromatic Hydrocarbons, 413
13.16 Fused-Ring Aromatic Hydrocarbons, 414
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Unsaturated Hydrocarbons:
Alkenes
Alkynes
Arenes
H
H
C
C
C
C
C
H
C
H
H
H
ethene
ethyne
benzene
C2H4
C2H2
C6H6
CnH2n
unsaturated
alkene
Chapters 13
CnH2n-2
unsaturated
alkyne
Chapters 13
CnHn
Aromatic
Arene
Chapter 13
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Units of Unsaturation:
Alkenes
Alkynes
Arenes
H
H
C
C
C
C
C
H
ethene
ethyne
C2H4
C2H2
CnH2n
CnH2n-2
Units of Unsaturation
CnH2n+2
CnH2n+2
(6-4)/2 =1
one double =
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(6-2)/2 =2
one triple 
C
H
H
H
benzene
C6H6
CnHn
CnH2n+2
(14-6)/2 =4
three double =
1 ring
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1. Write the name of names and units of
unsaturation for the hydrocarbons (alkane,
alkene, alkyne and arene) with following
general formula.
CnH2n+2 CnH2n CnH2n-2
Name
CnHn
a) ______ b) ____ c) ____ d) ___
Unit of unsat. a) ______ b) ____ c) ____ d) ___
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Isomerism
Isomers - different compounds having the same molecular formula but
different structural formulas
There are two type of Isomers:
Constitutional isomerism: Different connections among atoms in the
Skeleton
Position
Functional group
Stereoisomerism: Same connectivity among atoms, but these atoms differ
in spatial orientation
geometric
conformational
optical
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Constitutional Isomers
Skeletal (Chp. 12)
CH 3
CH 3CH 2CH 2CH 3
CH 3CHCH 3
Functional (Chp. 14)
Positional (Chp. 12)
CH 3CH 2OH CH 3OCH 3
CH 3CH 2CH 2 CH 3CH CH 3
Br
Br
Stereoisomers
Geometric (Chp. 13) Conformational (Chp.12)
H
H
C C
Br
Br
H
Br
C C
Br
H
CH 3
CH 3
CH 3
H
CH 3
H
H
H
HH
HH
Enantiomers (Optical) (Chp. 16)
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CO 2H
C
H
OH
CH 3
CO 2H
C
HO
H
CH 3
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2. Draw all constitutional isomers of
butane: C4H10.
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3. Names of following cycloalknes:
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4. Complete the following reactions of alkanes.
a) Combustion:
i) C5H12(g) +
8 O2(g)  ___CO2(g) + ___H2O(g)
ii) C4H10(g) + ___ O2(g)
 ___CO2(g) + ___H2O(g)
b) Halogenations:
(substitution reaction to form alkyl halides)
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Unsaturated hydrocarbons
• Hydrocarbons with carbon-carbon double
bonds and triple bonds
• double bonds: alkenes
• triple bonds: alkynes
• three alternating double bond in 6 carbon
ring: aromatics
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Unsaturated Hydrocarbons in Use
Beta-carotene is in carrots
Ethene is the hormone
that causes tomatoes to ripen.
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Acetylene: Welding
sex pheromones in insect control
involves luring insect into a trap.
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Unsaturated Hydrocarbons:
Alkenes
Alkynes
Arenes
H
H
C
C
C
C
C
H
C
H
H
H
ethene
ethyne
benzene
C2H4
C2H2
C6H6
CnH2n
unsaturated
alkene
Chapters 13
CnH2n-2
unsaturated
alkyne
Chapters 13
CnHn
Aromatic
Arene
Chapter 13
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Nomenclature of Alkenes: Common Names
Some alkenes, particularly low-molecular-weight ones, are known
almost exclusively by their common names
CH3
IUPA C:
Common:
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CH2 =CH2
CH3 CH=CH2
CH3 C=CH2
Ethene
Ethylene
Propene
Propylene
2-Methylprop ene
Isobutylene
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IUPAC Nomenclature of Alkynes
• use the infix -yn- to show the presence of a carboncarbon triple bond
• number the parent chain to give the 1st carbon of the
triple bond the lower number
• follow IUPAC rules for numbering and naming
substituents
2
4
1
3
3-Methyl-1-bu tyne
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1
2 3
4
5
6
7
6,6-D imethyl-3-heptyne
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Example of IUPAC Nomenclature of Alkenes Cycloalkanes
6
5
4
6
2
3
1
1-Hexen e
5
5
4
3
2
4
3
1
2
1
4-Meth yl-1-h exene
2-Ethyl-3-methyl1-p entene
2
4
3
5
CH3
3
4
1
2
3-Methylcyclopenten e
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1 CH 3
6 CH 3
1,6-D imeth ylcycloh exene
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Naturally Occurring
Alkenes Cis-Trans Isomerism
– vitamin A has five double bonds
– four of the five can show cis-trans isomerism
– vitamin A is the all-trans isomer
OH
Vitamin A (retinol)
enzymecatalyzed
oxidation
O
H
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Vitamin A aldeh yd e (retinal)
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Naturally Occurring Alkenes: The Terpenes
Terpene: a compound whose carbon skeleton can be divided into
two or more units identical with the carbon skeleton of isoprene
head
1
2
4
tail
3
2-Methyl-1,3-b utadiene
(Is oprene)
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Terpenes with isoprene units
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Terpenes: Polymers of Isoprene
• myrcene, C10H16, a
component of bayberry wax
and oils of bay and verbena
• menthol, from peppermint
OH
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Terpenes
Vitamin A (retinol)
the four isoprene units in vitamin A are shown in red
they are linked head to tail, and cross linked at one
point (the blue bond) to give the six-membered ring
OH
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5) How many isoprene units a in the
following natural product?
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6) Give common name or/and IUPAC names
of following compounds
a)
b)
c)
d)
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Cis and trans Geometrical isomers of alkenes
two groups are said to be located cis to each other if they lie
on the same side of a plane with respect to the double bond.
If they are on opposite sides, their relative position is
described as trans.
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Cis-Trans Isomerism
Dienes, trienes, and polyenes
for an alkene with n carbon-carbon double bonds, each of
which can show cis-trans isomerism, 2n cis-trans isomers
are possible
consider 2,4-heptadiene; it has four cis-trans isomers, two
of which are drawn here
Doub le bond
C2 -C3 C4 -C5
trans
trans
trans
cis
cis
trans
cis
cis
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2
4
t rans,t rans-2,4h eptadiene
4
trans ,cis-2,4h eptadiene
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6) Give common name or/and IUPAC names of
following compounds
e)
f)
g)
h)
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i)
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Physical Properties
• Alkenes and alkynes are nonpolar compounds
• the only attractive forces between their molecules
are dispersion forces
• Their physical properties are similar to those
of alkanes of similar carbon skeletons
• those that are liquid at room temperature are less
dense than water (1.0 g/m L)
• they dissolve in each other and in nonpolar
organic solvents
• they are insoluble in water
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Summary of Physical State of Unsaturated
Hydrocarbons
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Reactions of Unsaturated Hydrocarbons
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Chemical Reactions of Alkenes
1) Combustion: Alkenes are very flammable and the combustion products are
carbon dioxide and water.
2) Addition Reactions: Atoms or group of atoms are added to each a carbon
atom of a multiple bond. Two different reactants are involved.
a) Symmetric Addition Reactions:
Hydrogenation reaction: hydrogenation a hydrogen atom is added to each carbon
atom of a double bond. Catalyst (usually Ni or Pt) is needed.
Halogenation reaction: In alkene halogenation a halogen atom is added to each
carbon atom of a double bond. No catalyst is needed.
b) Asymmetric Addition Reactions: both reactants (H-X (X= Cl, OH)) and the alkene
need to be asymmetric
c) Polymerization of Alkenes: Addition Polymers
Polymers are macromolecules in which small units (monomers) are repeated again
and again.
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Markovnikov’s Rule
When an unsymmetrical molecule HQ (e.g., H-Cl, H-OH, H-F)
reacts with an unsymmetrical alkene, the hydrogen atom
from the HQ becomes attached to the unsaturated carbon
atom that already has the most hydrogen atoms
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Hydration
• Addition of water to the double bond.
Textbook page86.
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7) Complete the reactions of following alkenes
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7) Complete the reactions of following alkenes
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Polymerization
Formula
Name
Polypropylene
Monomer
CH3CH=CH2
Polymer
( CH-CH2 )
|
CH3
Polystyrene
-CH=CH2
Polychloroprene H2C=CHC=CH2
|
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Cl
( CH-CH2 )
( CH2CH=CCH2 )
|
Cl
39
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Aromatic hydrocarbons
• Aromatic hydrocarbons - organic compounds that
had aromas and had different chemical properties
from alkane
• Benzene is the parent compound for the aromatic
hydrocarbons. Textbook, page90.
• Consider benzene. C6H6
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Unsaturated Hydrocarbons cont’d
Space-filling and balland-stick models for the
structure of benzene.
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Resonance Structures of Benzene
• Resonance structures or contributing
structures = when two or more structure can
be drawn for a compound.
• In this case, the real structure is something
between the proposed structures.
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Naming Aromatic Hydroarbons.
Monosubstituted benzenes:
• Ar-CH2CH3 ethylbenzene
• Ar-CH2-CH2-CH2-CH3 butylbenzene
• Ar-CH3 (methylbenzene) toluene
• Ar-X (halobenzene) bromobenzene,
• Ar-NO2 nitrobenzene
• Ar-SO3H benzenesulfonic acid
• Ar-NH2 a nitrile substituent
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X
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Nomenclature
Disubstituted benzenes
locate substituents by numbering or
use the locators ortho (1,2-), meta (1,3-), and para (1,4-)
Where one group imparts a special name, name the
compound as a derivative of that molecule
CH3
NH2
COOH
NO2
Cl
Br
4-Bromotolu ene
3-Ch loroaniline
2-N itroben zoic acid
(p-Bromotoluen e) (m-Ch loroaniline) (o-N itrob enzoic acid)
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Nomenclature
Polysubstituted benzenes
– with three or more substituents, number the atoms of
the ring
– if one group imparts a special name, it becomes the
parent name
– if no group imparts a special name, number to give the
smallest set of numbers, and then list alphabetically
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Disubstituted benzenes:
•
•
•
•
•
•
•
2,6-dibromotoluene
p-diethylbenzene
3,5-dinitrotoluene
p-cholonitrobenzene
o-nitrobenzenesulfonic acid
4-benzyl-1-octene
m-cyanotoluene
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8) Match the following names of aromatic hydrocarbons (arenes)
to following structures: Anisole, Aniline, Phenol, Benzoic acid, Toluene,
Nitrobenzene. Complete the reactions of following alkenes
_________
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_________
_________ _________
_________
_________
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9. Give the names of the following disubstituted aromatic
hydrocarbons.
_________
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_________
_________
_________
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10) Complete the following chemical reactions of aromatic
hydrocarbons.
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