Organic Chemistry

Section 17.1 Nomenclature 673

Take a careful look at the following examples to make sure that you understand the
difference between systematic (IUPAC) and common nomenclature:

The functional group of a carboxylic acid is called a carboxyl group.

Carboxylic acids in which a carboxyl group is attached to a ring are named by adding
“carboxylic acid”to the name of the cyclic compound.

Acyl Halides
Acyl halidesare compounds that have a halogen atom in place of the OH group of a
carboxylic acid. The most common acyl halides are acyl chlorides and acyl bromides.
Acyl halides are named by using the acid name and replacing “ic acid”with “yl chlo-
ride”(or “yl bromide”). For acids ending with “carboxylic acid,”“carboxylic acid”is
replaced with “carbonyl chloride”(or “bromide”).

Acid Anhydrides
Loss of water from two molecules of a carboxylic acid results in an acid anhydride.
“Anhydride”means “without water.”

If the two carboxylic acid molecules forming the acid anhydride are the same, the
anhydride is a symmetrical anhydride. If the two carboxylic acid molecules are differ-
ent, the anhydride is a mixed anhydride. Symmetrical anhydrides are named by using
the acid name and replacing “acid”with “anhydride.”Mixed anhydrides are named by
stating the names of both acids in alphabetical order, followed by “anhydride.”

ROH

C

O

an acid anhydride

HO R

C

O

RRO

C

O

C

O

a carboxyl group

C

OH

O

COOH CO 2 H

carboxyl groups are frequently

shown in abbreviated forms

3-D Molecules:

trans-3-Methylcyclo-

pentanecarboxylic acid;

Acetic anhydride

CH 3 CH 2 CH OH

O

OH

O

CH 3 O

2-methoxybutanoic acid

-methoxybutyric acid

CH 3 CH 2 CHCH 2

Br

OH

O

CH 3 CH 2 CHCH 2 CH 2

Cl

3-bromopentanoic acid

-bromovaleric acid

4-chlorohexanoic acid

-chlorocaproic acid

systematic name:

common name:

C C C

trans-3-methylcyclopentanecarboxylic

acid

1,2,4-benzenetricarboxylic

acid

CH 3

COOH

COOH

COOH

COOH

O

C

OH

cyclohexanecarboxylic acid

CH 3

ethanoyl chloride

acetyl chloride

cyclopentanecarbonyl

chloride

CH 3 CH 2 CHCH 2

CH 3

3-methylpentanoyl bromide

-methylvaleryl bromide

C

O

systematic name:

common name:

Cl

C

O

Br

C

O

Cl