Write structures for the following compounds.(a) 3-ethyl-4-methylhexane (b) 3-ethyl-5-isobutyl-3-methylnonane(c) 4-tert-butyl-2-
methylheptane (d) 5-isopropyl-3,3,4-trimethyloctane
2 answers:
Answer:
Find attached answer to this question.
Explanation:
a. 4-Isopropyloctane has a chain of eight carbons, with an isopropyl group on the fourth carbon.
5-tert-Butyldecane has a chain of ten carbons, with a tert-butyl group on the fifth.
CH3
4-isopropyloctane
CHCH3 CH3
CH3 CH3CH2CH2CH2CH2CH2 CH
5-tert-butyldecane
CH3 CH3CH2CH2CH2CH2CH2CH2CH2 CH
CCH3 CH3
3-3 Nomenclature of Alkanes 93
di- means 2 tetra- means 4 hexa- means 6
tri- means 3 penta- means 5 hepta- means 7
b. Using this rule, we can construct names for some complicated structures. Let\u2019s fin-
ish naming the heptane on p. 90, shown here in the margin. This compound has an ethyl
group on C3 and three methyl groups on C2, C4, and C5. List the ethyl group alphabeti-
cally before the methyl groups, and give each of the four substituents a location number.
Problem-solving Hint
When substituents are alphabetized,
iso- is used as part of the alkyl group
name, but the hyphenated prefixes
are not. Thus, isobutyl is alphabetized
with i, but n-butyl, tert-butyl, and sec-
butyl are alphabetized with b. The
number prefixes di-, tri-, tetra-, etc.
are ignored in alphabetizing.
CH3 CH
2-bromobutane
Br
CH2CH3 CH3 CH
3-chloro-2-methylpentane
CH3 Cl
CH CH2CH3 CH3 CH
1,2-difluoropropane
F
CH2F
c. CH2CH(CH3)2CH2CH3
CH CHCH2 CH2 CH2CH3 CH3
S O LV E D P R O B L E M 3-2
Give a systematic (IUPAC) name for the following compound.
SOLUTION
The longest carbon chain contains eight carbon atoms, so this compound is named as an octane.
Numbering from left to right gives the first branch on C2; numbering from right to left gives
the first branch on C3, so we number from left to right.
CH CH2
CH3
CH CH CH2CH3
CH CH3
CH3
CH3
CH3
3-ethyl-2,4,5-trimethylheptane
7
65
4 3
2
1
CH3
CH3
CH3 CH3
CH3
CH3
CH3
CH
CH CH CH
CH2CH3
CH2
C
d. CH3 CH3
CH3
CH2 CH2 CH2 CH2 CH2
CH2
CH
CH3 CH3CH
CH
CH3 CH
Br CH2CH3
CH CH3(b)
CH3CH2
CH2CHCH3 CH3
Answer:
Here's what I get
Explanation:
(a) 3-Ethyl-4-methylhexane
The main chain is eight carbons long, with an ethyl group at C-3 and a methyl group at C-4
(b) 3-Ethyl-5-isobutyl-3-methylnonane
The main chain is nine carbons long, with an ethyl group and a methyl group on C-3 and an isobutyl group on C-5.
Note that the name isobutyl is acceptable in general use, but the preferred IUPAC name (PIN) for the group is now (since 2013) "2-methylpropan-2-yl".
The PIN for your compound is 3-ethyl-3-methyl-5-(2-methyl propan-2-yl)nonane.
(c) 4-<em>tert</em>-butyl-2-methylheptane
The main chain is seven carbons long, with a <em>tert</em>-butyl group at C-4 and a methyl group at C-2.
For some reason, the IUPAC has retained the name <em>tert</em>-butyl for the group, so the name you give is the PIN.
The prefix "<em>tert</em>" is written in italics.
(d) 5-isopropyl-3,3,4-trimethyloctane
The main chain is eight carbon atoms long, with two methyl groups on C-3 and one on C-4, and an isopropyl group on C-5.
The PIN for an isopropyl group is now "propan-2-yl", so the IUPAC name for your compound is 3,3,4-trimethyl-5-(propan-2-yl)octane.
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