CHEMISTRY 122
HW CH#3 ALKENES/ALKYNES
15,17,18,19,20,23,27,28, 32, 36, 37, 38, 42, 46, 48, 49,67.
3-15
See Appendix A13/14
3-17
See Appendix A13/14
3-18
In ethane, each carbon is surrounded by four regions of electron density; bond angles are
109.5°. In ethylene, each carbon is surrounded by three regions of electron density; bond
angles are 120
3-19
See Appendix A13/14
3-20
The bond angles around the circled atoms are estimated using the VSEPR theory.
109.5o
(a)
(b)
OH
120o
109.5o
120o
(b)
(d)
109.5o
180o
Br
109.5o
Br
3-23
See Appendix A13/14
3-27
See Appendix A13/14
3-28
The structural feature that makes cis-trans isomerism possible in alkenes is restricted
rotation about the carbon-carbon double bond. In cycloalkanes, it is restricted rotation
about the carbon-carbon bonds of the ring. These two structural features have in
common restricted rotation about carbon-carbon bonds.
3-32
The line-angle drawing of the all cis arachidonic acid:
COOH
Arachidonic acid
3-36
(a)
Four alkenes with molecular formula C5H10 do not show cis-trans isomerism.
CH3
CH3
CH3
CH2=CHCH2CH2CH3
CH2=CCH2CH3
CH2=CHCHCH3
CH3C=CHCH3
2-Methyl-2-butene
1-Pentene
2-Methyl-1-butene
3-Methyl-1-butene
(b) Only one alkene with molecular formula C5H10 shows cis-trans isomerism.
H3 C
H3 C
H
CH2CH3
C C
C C
H
CH2CH3
H
H
trans-2-Pentene
cis-2-Pentene
(c) Four cycloalkanes with molecular formula C5H10 do not show cis-trans
isomerism.
CH2CH3
H3C CH3
CH3
Cyclopentane
Methylcyclobutane
1,1-Dimethylcyclopropane
Ethylcyclopropane
(d) Only one cycloalkane with molecular formula C5H10 shows cis-trans
isomerism.
CH3
CH3
CH3
CH3
cis-1,2-Dimethyltrans-1,2-Dimethylcyclopropane
cyclopropane
3-37
See Appendix A13/14
3-38
(a), (b), and (c): True
no false statements
3-42
Cl
(a)
CH2CH3 + HCl
(b)
CH2CH3 + H2O
H2SO4
CH2CH3
OH
CH2CH3
I
(c) CH3(CH2)5CH=CH2 + HI
CH3(CH2)5CHCH3
CH3
CH2
CCl
(d)
C
+ HCl
CH3
CH3
OH
OH
H2SO4
(e) CH3CH=CHCH2CH3 + H2O
CH3CHCH2CH2CH3 + CH3CH2CHCH2CH3
OH
H2SO4
CH3CHCH2CH2CH3
(f) CH2=CHCH2CH2CH3 + H2O
12.46 (a)
12.48 (a)
and
and
3-67
See Appendix A13/14
(b)
(b)
(c)
(c)
and
3-49