Organic Compounds: Alkanes and Their Stereochemistry Answer Key

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Chapter 3
3.1 Identify the functional groups in each of the following molecules: O C

NH2

H N

O C

OH
H C CH2

(a)

(b)

O
(c) Solutions: a. b. c. d. Amide, double bond Amine, carboxylic acid Double bond, ketone, ester

O OCH3
(d)

CH2OH

Aromatic ring, double bond, alcohol (a) Alcohol (d) Amine (b) Aromatic ring (e) both ketone and amine (c) Carboxylic acid (f) two double bonds

3.2 Propose structures for simple molecules that contain the following functional groups:

Solutions: (a). H 3C
CH3

OH

(b).

O
(c). H3C (d). H 3C (e). (f). 3.3 Identify the functional groups in the following model of arecoline, a veterinary drug used to control worms in animals. Convert the drawing into a line-bond structure and a molecular formula.

OH
NH 2

CH3CH2COCH2CH2 NH2

Solution: Line-bond structure: Molecular formula: C8H13NO2 3.4 Draw structures of the five isomers of C6H14. Solution:

3.5 Propose structures that meet the following descriptions: (a) Two isomeric esters with the formula C5H10O2 (b) Two isomeric nitriles with the formula C4H7N Solution:

O C H3C
(a):
H2 C H3C H3C C H2 C N H3C CH C N

H2 C O C H2

CH3

H2 C H3C C O

O C H2

CH3

(b):

3.6 How many isomers are there with the following descriptions? (a) Alcohols with the formula C3H8O (b) Bromoalkanes with the formula C4H9Br Solution:

OH OH
(a): (b):4 3.7 Draw the eight 5-carbon alkyl groups(pentyl isomers). Solution H2C C H2 H2 C C H2 CH3 H3C H2 C C H2 CH3 H3C H2 C CH H2 C CH3

CH

H2 C C H2 CH CH3

CH3 H3C

CH CH CH3 CH3 H3C C CH3

CH3 H3C

H2 C C CH3

CH3

CH3 H3C C H2 CH C H2

H2 C

3.8 Identify the carbon atoms in the following molecules as primary, secondary, tertiary, or quaternary: Solution: (a) 1

CH3 H3C
1

C H
3

H2 C
2

H2 C
2

1

CH3

(b)
3 1

H3C H3C
1

H C C H
3

1

CH3 H2 C
2

H2 C
2

CH3
1

(c)

1

1

CH3 H3C
1

CH3 H2 C
2

C H
3

C
4

CH3
1

CH3
1

3.9 Identify the hydrogen atoms on the compounds shown in Problem 3.8 as primary, secondary, or tertiary. Solution: The hydrogen in red is primary hydrogens; in blue is secondary hydrogens; in green is tertiary hydorgens (a) (b) CH3

CH3CHCH2 CH2 CH3 H3CCHCH3

CH3CH2CHCH2CH3

(c)

CH3

CH3

CH3CHCH2CCH3
CH3

3.10 Draw structures of alkanes that meet the following descriptions: (a) An alkane with two tertiary carbons (b) An alkane that contains an isopropyl group (c) an alkane that has one quaternary and one secondary carbon CH3 3 CH Solution: (a) CH3CHCHCH3

(b)

CH3

CH3CHCH2CH3

(c)

CH3

CH3CCH2CH3
CH3

3.11 Give IUPAC names for the following compounds:
(a)

The three isomers of C5H12

CH3 H3CH2C CH CHCH3
(b)

CH2CH3

CH3
(c)

(H3C)2HCH2C CH CH3 CH3

(d)

(H3C)3CH2CH2C CH CH2CH3

Solution: H C (a)
3

C H
2

C H 2 C H
2

C H
3

Pentane

CH3 H3CH2C CH CH3 2-Methylbutane

CH3 H3C C CH3 CH3
(b) 3,4-Dimethylhexane (c) 2,4-Dimethylpentane (d) 2,2,5-Trimethylheptane 2,2-Dimethylpropane

3.12 Draw structures corresponding to the following IUPAC names: (a) 3,4-Dimethylnonane (b) 3-Ethyl-4,4-dimethylheptane (c) 2,2-Dimethyl-4-propyloctane (d) 2,2,4-Trimethylpentane Solution:

(a)

(b)

(c)

(d) 3.13 Name the eight 5-carbon alkyl groups you drew in problem 3.7. ( 3.7 Draw the eight 5-carbon alkyl groups.) Solution:

CH3 C H3C CH3 2,2-dimethylpropyl or neopentyl H2 C H3C CH H3C CH3 2-methylbutyl CH3 H3C H2 C C CH3 1,1-dimethylpropyl 1,2-dimathylpropyl H2 C C H2 H3C H2 C C H2 pentyl H2 C C H2 H3C

CH3 CH C H2 isopentyl or 3-methylbutyl CH3 H2 C C H2 1-ethylpropyl 1-methylbutyl CH3 CH H3C CH CH3 CH H3C H2 C CH H2 C CH3 H2 C

3.14 Give the IUPAC name for the following hydrocabon, and covert the drawing into a skeletal structure.

Solution:
CH3 H3C H2 C C CH3 CH3 C H H C CH3 H2 C CH3

3,3,4,5-Tetramethyl-heptane 3.15: Give the names of the following cycloalkanes.

Solution:

(a)...
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