CHEM 122: Introduction to Organic Chemistry
Chapter 3: Alkenes and Alkynes.
1. What is the difference in structure between a saturated hydrocarbon and an
unsaturated hydrocarbon?
2. Draw a structural formula for at least one bromoalkene with the molecular
formula C5H9Br that (a) shows cis/trans isomerism and (b) does not show
cis/trans isomerism.
3. Predict all bond angles about each circled carbon atom.
Br
OH
Br
a)
b)
c)
d)
4. Draw a structural formula for each compound.
a)
b)
c)
d)
e)
trans-2-Methyl-3-hexene
2-Methyl-3-hexyne
2-Methyl-1-butene
3-Ethyl-3-methyl-1-pentyne
2,3-Dimethyl-2-pentene
5. Write the IUPAC name for each unsaturated hydrocarbon.
CH 3
H3C
CH3
CH3
a) CH2=CH(CH2)4CH3
b)
d) (CH3)2CHCH=C(CH3)2
e) CH3(CH2)5C CH
f) CH3CH2C CC(CH3)3
g)
c)
CH 3
6. Write the IUPAC name for each unsaturated hydrocarbon.
a)
b)
CH2
CH3CH2CH2
c) CH3CH2CCH3
d)
C=CH2
CH3CH2CH2
7. Explain why each name is incorrect and then write a correct name.
a)
b)
c)
d)
e)
f)
1-Methylpropene
3-Pentene
2-Methylcyclohexene
3,3-Dimethylpentene
4-Hexyne
2-Isopropyl-2-butene
8. What structural feature in alkenes makes cis-trans isomerism in them possible?
What structural feature in cycloalkanes makes cis-trans isomerism in them
possible? What do these two structural features have in common?
9. Which of these alkenes shoe cis-trans isomerism? For each that does, draw
structural formulas for both isomers.
a)
b)
c)
d)
e)
f)
1-Hexene
2-Hexene
3-Hexene
2-Methyl-2-hexene
3-Methyl-2-hexene
2,3-Dimethyl-2-hexene
10. Following is the structural formula of a naturally occurring unsaturated fatty acid.
CH3(CH2)7CH=CH(CH2)7COOH
The cis stereoisomer is named oleic acid, and the trans isomer is named elaidic
acid. Draw a line-angle formula of each acid, showing clearly the configuration
of the carbon—carbon double bond in each.
11. Name and draw structural formulas for all compounds with the molecular formula
C5H10 that are:
a)
b)
c)
d)
Alkenes that do not show cis-trans isomerism
Alkenes that show cis-trans isomerism
Cycloalkanes that do not show cis-trans isomerism
Cycloalkanes that show cis-trans isomerism
12. -Ocimene, a triene found in the fragrance of cotton blossoms and several
essential oils, has the IUPAC name cis-3,7-dimethyl-1,3,6-octatriene. (Cis refers
to the configuration of the double bond between carbons 3 and 4, the only double
bond in this molecule about which cis-trans isomerism is possible.) Draw a
structural formula for -ocimene.
13. What reagent and/or catalysts are necessary to bring about each conversion?
Br
a) CH3CH=CHCH3
CH3
b) CH3C=CH2

CH3CH2CHCH3
CH3

CH3CCH3
OH
I
c)
CH3
d) CH3C=CH2
CH3

CH3C—CH2
Br
Br
14. Draw structural formulas for all possible carbocations formed by the reaction of
each alkene with HCl. Label each carbocation as primary, secondary, or tertiary.
CH3
a) CH3CH2C=CHCH3
b) CH3CH2CH=CHCH3
CH3
CH 2
c)
d)
15. Complete these equations.
+
CH 2 CH 3
a)
+
CH2CH3
HCl
H2SO4
H2O
b)

c) CH3(CH2)5CH=CH2 + HI
CH 2
+
C
HCl
CH 3
d)
H2SO4
e) CH3CH=CHCH2CH3 + H2O
H2SO4
f) CH2=CHCH2CH2CH3 + H2O
16. Draw a structural formula for the product of each reaction.
a) 1-Methylcyclohexene + Br2 
b) 1,2-Dimethylcyclopentene + Cl2 
17. Draw a structural formula for an alkene with the indicated molecular formula that
gives the compound shown as the major product. Note that more than one alkene
may give the same compound as the major product.
CH3
H2SO4
a) C5H10
+
H2 O
CH3CCH2CH3
OH
CH3
b) C5H10 + Br2

CH3CHCHCH2
Br
Br
CH 3
c) C7H12 + HCl

Cl
18. Draw a structural formula for an alkene with the molecular formula C5H10 that
reacts with HCl to give the indicated chloroalkane as the major product. More
than one alkene may give the same compound as the major product.
CH3
CH3
a) CH3CCH2CH3
Cl
b) CH3CHCHCH3
c) CH3CHCH2CH2CH3
Cl
Cl
19. With the notable exception of ethanol, the acid-catalyzed hydration of alkenes
cannot be used to prepare primary alcohols. It can only be used to prepare
secondary and tertiary alcohols from alkenes in good yield. Explain why this is
so and illustrate your reasoning with specific examples.
20. Draw the structural formula of an alkene that undergoes acid-catalyzed hydration
to give the indicated alcohol as the major product. More than one alkene may
give each alcohol as the major product.
a)
b)
c)
d)
3-Hexanol
1-Methylcyclobutanol
2-Methyl-2-butanol
2-Propanol
21. Draw the product formed by treatment of each alkene with H2/Ni.
H3C
a)
H
C=C
H
H
b)
CH2CH3
H
C=C
H3C
CH2CH3
CH 3
c)
d)
22. Hydrocarbon A, C5H8, reacts with 2 moles of Br2 to give 1,2,3,4-tetrabromo-2methylbutane. What is the structure of hydrocarbon A?
23. Show how to convert 1-butene to these compounds
a)
b)
c)
d)
Butane
2-Butanol
2-Bromobutane
1,2-Dibromobutane
24. Draw the structural formula for a cycloalkane with the molecular formula C6H10
that reacts with Cl2 to give each compound.
Cl
Cl
H3C
Cl
a)
Cl
b) Cl
Cl
Cl
CH 3
c)
CH 2 Cl
d)
25. Propose a structural formula for the product(s) when each of the following
alkenes is treated with H2O/H2SO4. Why are two products formed in part (b) but
only one in parts (a) and (c)?
a) 1-Hexene gives one alcohol with a molecular formula of C6H14O.
b) 2-Hexene gives two alcohols, each with a molecular formula of C6H14O.
c) 3-Hexene gives one alcohol with a molecular formula of C6H14O.
26. cis-3-Hexene and trans-3-hexene are different compounds and have different
physical and chemical properties. Yet, when treated with H2O/H2SO4, each gives
the same alcohol. What is this alcohol, and how do you account for the fact that
each alkene gives the same one?
27. Draw the structural formula of an alkene that undergoes acid-catalyzed hydration
to give each of the following alcohols as the major product. More than one alkene
may give each compound as the major product.
CH3
CH 3
OH
OH
OH
OH
a)
b)
c)
CH3
d)