Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Solving Problems: A Chemistry Handbook
Chemistry: Matter and Change
217
SOLVING PROBLEMS:
A CHEMISTRY HANDBOOK
CHAPTER 21
the lowest possible set of numbers for the substituents. The following example problem shows you how to name a substituted
cycloalkane.
Example Problem 21-2
Naming Substituted Cycloalkanes
Name the cycloalkane shown.
a. The ring has five carbon atoms, so the parent name is
cyclopentane.
b. There are four substituent groups. A methyl group and an ethyl
group are attached to the same carbon atom, and another ethyl
group is also bonded to the ring. You may be unfamiliar with
the fourth substituent group, which is called an isopropyl group.
c. Assign position number 1 to the carbon atom with two substituents. There are two ways to number the rest of the ring.
Both numbering methods place branches at positions 1, 1, 3,
and 4. Should the ethyl group or the isopropyl group be
assigned position 3? The ethyl group is assigned position 3
because ethyl precedes isopropyl in alphabetical order. The
isopropyl group is assigned position 4. The numbering on the
left is correct. The name of the compound is 1,3-diethyl-4isopropyl-1-methylcyclopentane.
CH 2 CH 3
CH 3 CH 2 CH 3 CHCH 3
CH 3
CH 2 CH 3
CH 3 CH 2 CH 3 CHCH 3
CH 3
1
5
2
4
3
1
2
5
3
4
CH 2 CH 3
CH 3 CH 2 CH 3 CHCH 3
CH 3