CHAPTER
3
An Introduction to Organic Compounds:
Nomenclature, Physical Properties, and Representation of Structure
1.
a. n-propyl alcohol or propyl alcohol
b. dimethyl ether
c. z-propylamine or propylamine
2.
Notice that each carbon forms four bonds and each hydrogen and bromine forms one bond.
CH3
CH3CH2CH2CH2Br
n-butyl bromide
or
butyl bromide
CH3CHCH2CH'I
I
.
Br
see-butyl bromide
I
I
CH3CCH3
CH:,!CHCH2Br
.I
CH3
isobutyl bromide
Br
tert-butyl bromide
CH3
I .
3.
a. CH3CHOH
c.
CH3CH20CH2CH2CH3
I
I
CH3
CH3
b. CH3CHCH2CH2F
I
CH3
e. CH3CNH2
d. CH3CH2CHI
f. CH3CH2CH2CH2CH2CH2CH2CH2Br
I
CH3
23
24
Chapter 3
CH3
CH'j
I -
7.
a. #1
CH3CH2CH2CH2CH2CH2CH2CH3
2, 5-dimethylhexane
octane
CH3
CH'j
CH3CHCH2CH2CH2CH2CH3
#10 CH3CH2CH - CHCH2CH3
3,4-dimethylhexane
2-methylheptane
CH'j CH:~
CH3
I -
#3
CH
I - I 3-
I -
#2
I
#9 CH3CHCH2CH2CHCH3
I - I -
CH3CH2CHCH2CH2CH2CH3
#11 CH3C-CHCH2CH3
I
CH3
2,2,3-trimethylpentane
3-methylheptane
CH3 CH1
CH'j
I -
#4
CH3CH2CH2CHCH2CH2CH3
I
-I
1-
#12 CH'jCCH2CHCH3
CH3
4-methylheptane
2,2,4-trimethylpentane
CH3
#5
I CH3CCH2CH2CH2CH'j
-I
-
CH'j
CH
I - I 3-
#13 CH3CH-CCH2CH3
I
CH3
CH3
2,3,3-trimethylpentane
2,2-dimethylhexane
CH'j
#6
I -
CH3
CH3CH2CCH2CH2CH'j
#14 CH3CH-CH-CHCH3
I
CH3
I -
I
-
CH3
I -
CH3
3,3-dimethy Ihexane
CH3
CH
I - I 3-
#7
CH3CH-CHCH2CH2CH3
2,3,4-trimethylpentane
CH3 CH1
I - I -
#15 CH3C-CCH'j
I
I
-
CH3 CH3
2,3-dirnethy lhexane
CH1
I -
#8
2,2,3,3-tetrarnethylbutane
CH3
I .
CH3CHCH2CHCH2CH3
#16 CH3CH2CHCH2CH2CH3
I
CH2CH3
2,4-dimethylhexane
3-ethy lhexane
-
Chapter 3
CH3
CH"
I
#17 CH3CH2CHCHCH3
I
#18
-
CH2CH3
3-ethy 1-2-methy lpentane
I CH1CH2CCH2CH3
I
CH2CH3·
3-ethyl- 3-methy lpentane
b. The systematic names are under the compound.
c. #2,#7,#8,#9,#12,#13,#14,#17
d. #3,#8,#10,#11
~
8.
#5,#11,#12,#15
a. 2,2,4-trimethylhexane
d. 2,5-dimethylheptane
b. 2,2-dimethylbutane
e. 4-isopropyloctane
c. 3,3-diethylhexane
f.
4-ethyl-2,2,3-trimethylhexane
9.
{3
I
N
~2
OH
10.
c.·~
a.~OH
Br
d··~O/
b.~
11.
menthol
12.
a.
=
CIOH200
1-ethyl-2-methylcyclopentane
b. ethylcyclobutane
terpin hydrate = CIOH2002
c. 3,6-dimethyldecane
d. 5-isopropylnonane
25
26
Chapter 3
13.
a. Both compounds have the same name (l-bromo-3-methylhexane),
compound.
so they are the same
b. Both compounds have the same name (1-iodo-2-methylcyclohexane),
compound.
14.
c. cyclohexyl bromide
a. see-butyl chloride
2-chlorobutane
bromocyclohexane
d. isopropyl fluoride
b. isohexyl chloride
l-chloro-4-methylpentane
2-fluoropropane
15.
a. a tertiary alkyl bromide
b.
a tertiary alcohol
16.
a. methy lpropy lamine
c.
diethylamine
secondary
d.
buty ldimethy lamine
tertiary
secondary
h. trimethylamine
tertiary
17.
a.
eSel
so they are the same
c.
c.
.
.
a pnmary amme
&CI &CI
CH3
Cl
18.
a. The bond angle is predicted to be similar to the bond angle in water (~104.5°).
b. The bond angle is predicted to be similar to the bond angle in ammonia (~107.3°).
c. The bond angle is predicted to be similar to the bond angle in water (~l 04.5°).
19.
Room temperature is about 25°C. Therefore, pentane, with a boiling point of 36 °C is the
smallest alkane that is a liquid at room temperature.
20.
a. An 0 - H hydrogen bond is longer.
b. Because it is shorter, an 0 - H covalent bond is stronger.
Chapter 3
21.
a. 1,4, and 5
b. 1,2,4,5,
and 6
OH
22.
OH
HO~OH
>
~>
23.
27
OH
~OH
>
NH2
~
>
~
>
~
a. cH3cH2cH2cH2cH2CH2Br
>
b. CH3CH2CH2CH2CH2CH2CH2CH2CH3
CH3CHCH2CH2CH2CH2CH"
.
1
.
>
CH3
c. CH3CH2CH2CH2CH20H
CH3CH2CH2CH2CH2Br
>
>
CH3CH2CH2CH2Br
CH3CH2CH2CH2CH2CH2CH2CH3
H3C
CH3
H3C
CH3
>
·1 I·
CH3C-CCH3
.I I .
> CH3CH2CH2CH20H
> CH3CH2CH2CH2CI
> CH3CH2CH2CH2CH3
24.
Figure 3.2 in the text shows that even number alkanes have higher melting points than odd
number alkanes. Therefore, since more energy is required to disrupt the crystal lattice of even
numbered alkanes, we can conclude that even number alkanes pack more tightly.
25.
a.
b.
26.
HOCH2CH2CH20H
0
>
CH3CH2CH20H
OH
>
6
>
0
>CH3CH2CH2CH20H
>
CH3CH2CH2CH2CI
The amine is more soluble
than the alcohol in water,
because the amine has two
hydrogens that can form
hydrogen bonds with water
and the alcohol has only one.
Because cyclohexane is a nonpolar compound, it will have the lowest solubility in the most polar
solvent, which, of the solvents given, is ethanol.
CH3CH2CH2CH2CH20H
l-pentanol
CH3CH20CH2CH3
diethyl ether .
CH3CH20H
ethanol
CH3CH2CH2CH2CH2CH3
hexane
28
Chapter 3
27.
Hexethal would be expected to be the more effective sedative because it is more nonpolar than
barbital since hexethal has a hexyl group in place of the ethyl group of barbital. Being more
nonpolar, hexethal will be better able to penetrate the nonpolar membrane of a cell.
28.
a.
b. yes
c. yes
1
29.
b.
a. H~H
4
CH3
CH~C 2
2
HyH
H
H
CH2CH:~
30.
5
Cl
3
H
H
axial
c0-CI
equatorial
31.
At anyone time, there will be more molecules of isopropylcyc1ohexane with the substituent in
the equatorial position because the isopropyl substituent is larger than the ethyl substituent.
Because the isopropyl substituent is larger, the axial confomer of isopropylcyclohexane has more
steric strain than the axial conformer of ethylcyclohexane, so the isopropyl group will have a
greater preference for the equatorial position.
32.
a.
33.
a. ~CH2CH3
CIS
b.
C1S
c. trans
d. trans
CH3
c. trans-l-Ethyl-2-methylcyclohexane
is more stable because both substituents are in equatorial
positions, whereas cis-l-ethyl-2-methylcyclohexane
has one substituent in the equatorial
position and the other in the axial position.
Chapter 3
34.
Both Kekule and skeletal structures are shown.
CH3
1
a.
1
1
f.
CH,CH?CHOCCH3
-
-I
-
CHCH3
CH3
1
CH3CH2CH2CHCHCH2CH2CH2CH3
-
1
CH3 CH3
CHCH3
1
CH3
~OX
e.
.Cf
Bf
3
CH
CH3
•
J.
1
CH3CHCH2CH2CCH2CH2CH3
- 1
1
Cf
-
Bf
CH3
Br
Br
29
30
Chapter 3
35.
a. 5-bromo-2-methyloctane
d. 3,3-diethylpentane
b. 2,2,6-trimethylheptane
e. isopropylcyclohexane
c. 2,3,5-trimethylhexane
f. N,N-dimethy J eye lohexanamine
36.
a. 3
c. 3
b. 6
CH1
I . CHl
I .
CH3CH-CCH:~
b.
I .
CH3
I .
37.
a.
CH3CHCH2CH2CH2CH3
CH3
2,2,3-trimethylbutane
2-methy Ihexane
38.
The first conformation is the most stable because the three substituents are more spread out, so
its gauche interactions will not be as large - the Cl in the first conformation is between a CH3
and an H, whereas the Cl in the other two conformers is between two CH3 groups.
39.
a. diethylpropylamine
c. isopenty lpropy lamine
TERTIARY
SECONDARY
d. cyclohexylamine
b. see-butylisobutylamine
PRIMARY
SECONDARY
CH3CH3
40.
41.
a.
0
a. l-ethoxypropane
ethyl propyl ether
b. 4-methyl-l-pentanol
b.
I
I
I
I
CH3C-CCH1
see-butyl chloride
e. 2-methylpentane
isohexane
42.
a. I-bromohexane
b. pentyl chloride
CH3CHCH2CHCH3
I
CH~
.'
I
CH3
f. 2-bromo-2-methylbutane
tert-pentyl bromide
g. cyclohexanol
cyclohexyl alcohol
h. bromocyclopentane
cyclopentyl bromide
see-butylamine
d. 2-chlorobutane
c.
CH3CH3
isohexyl alcohol
c. 2-butanamine
.
i.
3-propanamine
isopropylamine
j. 3-methyl-N-propyl-l-butanamine
see-butylethylamine
c. butyl alcohol
d. hexyl alcohol
e. hexane
f. pentyl alcohol
Chapter 3
43.
a.
~f~-r
CH3
b.
H3C~CH3
H3C~CH3
H3C
ru
CH3
31
CH3
44.
Ansaid is more soluble in wat,er. It has a fluoro substituent that can hydrogen bond to water.
Motrin has a nonpolar isobutyl substituent in place of Ansaid's fluoro substituent.
45.
Only one is named correctly.
d. correct
e. 2,5-dimethylheptane
f. 2,3,3-trimethyloctane·
a. 3-ethyl-2-methyloctane
b. 4-ethyl-2,2-dimethylheptane
c. l-bromo-3-methylbutane
46.
B has the highest energy (is the least stable). They are all diaxial-substituted cyclohexanes, so
each one has four 1,3-diaxial interactions. Only B has a 1,3-diaxial interaction between CH3 and
CI, which will be greater than a 1,3-diaxial interaction between CH3 and H or a 1,3-diaxial
interaction between CI and H.
47.
The only one is 2,2,3-trimethylbutane.
CH3CH3
I 'I
,I
CH3C-CHCH'l
CH3
48.
'
>y
c.
a.
boQ
49.
a.
l-bromopentane
b. butyl alcohol
.r:
d.
d.
isopentyl alcohol (it has stronger hydrogen bonds)
e.
hexylamine (it has more hydrogen bonds)
c. octane
50.
Alcohols with low molecular weights are more water soluble than alcohols with high molecular
weights because, as a result of having fewer carbons, they have a smaller nonpolar component
that has to be dragged into water.
32
Chapter 3
CH,
I -
51.
b.
a. H~H~
HyH
CH2CH3
most stable
c. Rotation can occur about all the C-C bonds. There are six carbon-carbon bonds in the
compound, so there are five other carbon-carbon bonds, in addition to the C3-C4 bond, about
which rotation can occur.
CH -CH-CH,-CH
I
3
~
2
-CH
2
-CH
3
CH3
d. Three of the carbon-carbon bonds have staggered conformers that are equally stable because
each is bonded to a carbon with three identical substituents.
il
CH -CH-CH
~I
2
-CH
2
-CH
il
2
-CH
3
CH3
52.
C and D are cis isomers. (In C, both substituents are downward pointing; in D, both substituents
are upward pointing.)
53.
a. CH3cH2cH2cH2CH2Br
CH,CH2CH2CHCH3
.
I
1 -bromopentane
primary alkyl halide
2 -bromopentane
secondary alkyl halide
3 -bromopentane
secondary alkyl halide
1 -bromo-3-methylbutane
primary alkyl halide
1 -bromo-2-methylbutane
primary alkyl halide
2 -bromo-2-methylbutane
tertiary alkyl halide
Br
CH3CH,CHCH2CH3
.
~I
Br
CH,
I .
CH3CHCH2CH2Br
CH,
I -
CH3CH2CHCH2Br
Br
I
I
CH3CH2CCH3
-
CH3
-
Chapter 3
Br
I
CH3CHCHCH'l
I
.
2 -bromo-3-methylbutane
secondary alkyl halide
1 -bromo-2,2-dimethylpropane
primary alkyl halide
CH3
CH3
I .
CH3CCH2Br
I
CH3
b. Four isomers are primary alkyl halides.
c. Three isomers are secondary alkyl. halides.
d. One isomer is a tertiary alkyl halide.
54.
a. butane
d. 6-chloro-4-ethyl-3-methyloctane
b. I-propanol
e. 6-isobutyl-2,3-dimethyldecane
c. 5-isopropyl-2-methyloctane
55.
a.
~CH2CH3
H3C
more stable
n
CH3
CH2CH3
~H3h
b. ~CH2CH3
CH(CH3)2
CH2CH3
more stable
c.
~CH2CH3
CH3
~
CH2CH3
more stable
CH3
d. ~CH2CH3
-9
H3C
more stable
e.
f.
~CH2CH3
CH2CH3
n
(CH3hCH
more stable
(CH3hCH
P-CH2CH3
(CH3)2C~
(CH3hCH
CH2CH3
more stable
CH2CH3
33
34
Chapter 3
56.
a. Each water molecule has two hydrogens that can form hydrogen bonds, whereas each alcohol
molecule has only one hydrogen that can form a hydrogen bond. Therefore, there are more
hydrogen bonds between water molecules than between alcohol molecules.
:O-H----:O-H
I
H
I
H
I
I
:O-H
I
H
:O-CHl
I
-
H
I
I
I
I
:O-CH
I
3
H
b. Each water molecule has two hydrogens that can form hydrogen bonds, whereas each
ammonia has three hydrogens that can form hydrogen bonds. However, oxygen is more
electronegative than nitrogen, so the hydrogen bonds between water molecules are stronger
than the hydrogen bonds between ammonia molecules. Because the number of hydrogen
bonds supports ammonia as having the higher boiling point but the strength of the hydrogen
bonds supports water, we could not have predicted which would have the higher boiling point.
However, being told that water has the higher boiling point we can conclude that the greater
electronegativity of oxygen compared to nitrogen is more important than the number of
hydrogens that can form hydrogen bonds.
c. Each water molecule has two hydrogens that can form hydrogen bonds, whereas each
molecule of hydrogen fluoride has only one hydrogen that can form a hydrogen bond.
However, fluorine is more electronegative than oxygen. Again we cannot predict which will
have the higher boiling point, but we can conclude from the fact that water has the higher
boiling point that in this case the greater number of hydrogens that can form hydrogen bonds
is more important than the greater electronegativity of fluorine compared to oxygen.
57.
Six ethers have molecular formula C5HI20.
CH30CH2CH2CH2CH3
/o~
ethyl propyl ether
l-ethox ypropane
butyl methyl ether
I-methoxybutane
see-butyl methyl ether
2- methox ybu tane
CH3
I -
CH3CH20CHCH3
/"--oA
ethyl isopropyl ether
2-ethoxypropane
tert-butyl methyl ether
2-methoxy-2-methylpropane
isobutyl methyl ether
I-methoxy-2-methylpropane
Chapter 3
58.
35
The most stable conformer has two CH3 groups in equatorial positions and one in an axial
position. (The other conformer would have two CH3 groups in axial positions and one in an
equatorial position.)
.
CH1
H3C~
H3C
59.
a. 3-ethyl-2,5-dimethylheptane
60.
Dibromomethane
b.
1,4-dichloro-5-methylheptane
does not have constitutional isomers.
If carbon were flat, the two structures shown below would be constitutional isomers, because the
Br's would be 90° apart in one compound and 180° apart in the other compound, so they would
be different compounds. However, since carbon is tetrahedral the two structures are identical, so
dibromomethane does not have constitutional Isomers.
H
Br
I
H-C-Br
I
I
H-C-H
I
Br
Br
CH20H
61.
HO~O\
HO~OH
OH
CH
I
62.
#1 CH3CH2CH2CH2CH2CH2CH3
heptane
3
#4 CH3CCH2CH2CH3
I
. CH3
2,2-dimethylpentane
CH1
CH1
I .
I .
#2 CH3CHCH2CH2CH2CH3
#5 CH3CH2CCH2CH1
I
2-methylhexane
.
CH3
3,3-dimethylpentane
CH1
I .
#3 CH3CH2CHCH2CH2CH3
3-methylhexane
CH3
CH3
I . I
#6 CH3CH-CHCH2CH3
2,3-dimethylpentane
36
Chapter 3
CH-~ CH-~
I 1#7 CH3CHCH2CHCH3
#9 CH1CH2CHCH2CH-'l
-
I
2,4-dimelhylpentane
-
CH2CH3
3-ethylpentane
CH3
CH3
I
1-
#8 CH3C-CHCH1
I
-
CH3
2,2,3-trimethylbutane
63.
The most stable conformer has all the substituents in equatorial positions.
CI
CI~CI
CI~Cl
CI
H$CH2CH3
CH3
I
64.
a.
5
CH
4
CH31li
3
H
H
H
2
H
H
~CH2CH3
H
H
H
H
A
C
CH1
CH3C*H
H~:
H
CH2CH3
H
CH3CH2
H
H
F
E
D
b.
H
B
Hx!XH
H
HCH3
A
A
c
r
E
Pontential
energy
I
B
F
D
60
0
65.
a.
Hx!XCH3
H
H
CH3CH2
120
180
Degrees of Rotation
b.
240
300
H~H
H
CH3
CH2CH3
360
Chapter 3
37
66.
a. one equatorial and one axial
b. both equatorial and both axial
c. both equatorial and both axial
d. one equatorial and one axial
e. one equatorial and one axial
f. both equatorial and both axial
67.
Both trans-l ,4-dimethylcyc1ohexane and cis-l-tert-butyl- 3-methylcyc1ohexane have a conformer
with two substituents in the equatorial position and a conformer with two substituents in the axial
position. cis-l-tert-Butyl-3-methyIcyc1ohexane
will have a higher percentage of the conformer
with two substituents in the equatorial position, because the bulky tert-butyl substituent will have
a greater preference for the equatorial position.