轻化工程专业英语(染整方向)(第2版)
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4.3 Carboxylic Acids

4.3.1 Sources of Carboxylic Acids

Many carboxylic acids were first isolated from natural sources and were given names based on their origin. Formic acid (Latin formica,"ant") was obtained by distilling ants. Since ancient times acetic acid (Latin acetum,"vinegar") has been known to be present in wine that has turned sour. Butyric acid (Latin butyrum,"butter") contributes to the odor of rancid butter,and lactic acid (Latin lac,"milk") has been isolated from sour milk.

4.3.2 Carboxylic Acid Nomenclature

Nowhere in organic chemistry are common names as prevalent as they are among carboxylic acids. Many carboxylic acids are better known by common names than by their systematic names,and the framers of the IUPAC nomenclature rules have taken a liberal view toward accepting these common names as permissible alternatives to the systematic ones.The following table lists both the common and the systematic names of some carboxylic acids.

Systematic names for carboxylic acids are derived by counting the number of carbons in the longest continuous chain that includes the carboxyl group and replacing the-e ending of the corresponding alkane by-oic acid. The first three acids in the table,methanoic (1 carbon),ethanoic (2 carbons),and octadecanoic acid (18 carbons),illustrate this point. When substituents are present,their locations are identified by number; numbering of the carbon chain always begins at the carboxyl group. This is illustrated in entries 4 and 5 in the table.

Note that compounds 4 and 5 are named as hydroxy derivatives of carboxylic acids,rather than as carboxyl derivatives of alcohols. We have seen earlier that hydroxyl groups take precedence over double bonds,and double bonds take precedence over halogens and alkyl groups in naming compounds. Carboxylic acids outrank all the common groups we have encountered to this point.

Double bonds in the main chain are signaled by replacing the-aneending of the corresponding alkane with-enoic acid,and their position is designated by a numerical prefix. Entries 6 and 7 are representative carboxylic acids that contain double bonds. Double-bond stereochemist is specified by using either the cis-trans or the E-Z notation.

When a carboxyl group is attached to a ring,the parent ring is named (retaining the final-e) and the suffix-carboxylic acidis added,as shown in entries 8 and 9.

Compounds with two carboxyl groups,as illustrated by entries 10 to 12,are distinguished by the suffix-dioic acidor-dicarboxylic acidas appropriate. The final-e in the base name of the alkane is retained.

The Systematic and the Common Names of Some Carboxylic Acids