7.6: Carboxylic Acids

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By the IUPAC system, the suffix -oic is added to the prefix identifying the hydrocarbon chain that includes the carboxyl carbon:

Left: C H 3 C H 2 C O 2 H. Labeled propanoic acid. Middle: C H 3 C H double bonded C H C H C O 2 H. Carbon 2 has a C H 3 substituent. Labeled 2-methyl-3-pentenoic acid. Right: H O 2 C C H 2 C (single bonded to N O 2) and single bonded to H C O 2 H. Labeled 2-nitrobutanedioic acid.

Situations arise when it is necessary to consider the parent as a one-carbon chain. In such circumstances, \(RCO_2H\) becomes a substituted carboxylic acid. This variation is met most frequently when \(R\) is a cycloalkyl or aryl group:

The substituent name for \(-CO_2H\) is carboxy:

H O C C H 2 C (with C O 2 H substituent) H C H 2 C O 2 H. Labeled 3-carboxypentanedioic acid.

For salts of carboxylic acids, the -oic suffix of the acid becomes -oate with the counter ion named as a separate word:

Left: C H 3 C double bonded to O and single bonded to O minus N H 4 plus. Labeled ammonium ethanoate (ammonium acetate). Right: C H 3 C (with N H 2 substituent) H C double bonded to O and single bonded to O minus and N A plus. Labeled sodium 2-aminopropanoate.

Contributors and Attributions

John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."