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Solutions for Structure and Stereochemistry of Alkanes
5 continued
(e) incorrect: 2-bromo-3-ethylbutane
The longest chain was not identified.
Br
4
3
21
correct: 2-bromo-3-methylpentane
INCORRECT CORRECT
Br
4
3
21
5
(f) incorrect: 2-diethyl-3-methylhexane
This name has two problems: two ethyl groups 
require two position numbers, presumably both 2 
but it is ambiguous; and the longest chain was not 
identified.
1
2
3 4
5
correct: 3-ethyl-3,4-dimethylheptane
6
1
3
4 5
6 7
2
INCORRECT CORRECT
2,3-dimethylbutane2,2-dimethylbutane3-methylpentane2-methylpentane
hexane
(or n-hexane)
(a)
2,2,3-trimethylbutane3-ethylpentane2,4-dimethylpentane2,3-dimethylpentane3,3-dimethylpentane
2,2-dimethylpentane3-methylhexane2-methylhexane
heptane
(or n-heptane)
(b)
CH2CHCH3
CH3
CHCH3
CH3
CHCH2CH3
CH3
2°
1-methylpropyl
common name = sec-butyl, 
abbreviation for secondary-butyl
2-methylpropyl
common name = isobutyl
1-methylethyl
common name = isopropyl
(c)(b)(a)
7 For this problem, the carbon numbers in the substituents are indicated in italics. The bold bond shows the 
point of attachment.
1 2 1 2 3 1 2 3
6 (Hints: systematize your approach to these problems. For the isomers of a six-carbon formula, for 
example, start with the isomer containing all six carbons in a straight chain, then the isomers containing a 
five-carbon chain, then a four-carbon chain, etc. Carefully check your answers to AVOID DUPLICATE 
STRUCTURES.)
C
CH3
CH3
CH3
3°
1,1-dimethylethyl
common name = tert-butyl or t-
butyl, abbreviation for tertiary-butyl
(d)
1 2
3-methylbutyl
common name = isopentyl or isoamyl
(e)
1 2
CH2CH2CHCH3
CH3
3 4
58