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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:

    Left: Cyclopropane with C O 2 H substituent. Labeled cyclopropane-carboxylic acid. Middle: Cyclohexane molecule with carbons labeled 1 through 6. C O 2 H substituents on carbons 1 and 2. Double bond between carbons 5 and 6. Labeled 4-cyclohexene-1,2-dicarboxylic acid. (Notice numbering to give the carboxylic groups the lowest numbers.) Right: Benzene ring with C O 2 H substituent. Labeled benzenecarboxylic acid (benzoic acid).

    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."

    This page titled 7.6: Carboxylic Acids is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by John D. Roberts and Marjorie C. Caserio.

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