7.5: Ketones, RCOR'

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The IUPAC system employs the suffix -one added to the prefix identifying the longest carbon chain of \(RCOR'\) that includes the carbonyl group. The chain is numbered to give the carbonyl group. The chain is numbered to give the carbonyl group the lowest possible number. In the examples given, the names in parentheses correspond to a less systematic nomenclature of ketones by which the \(R\) groups each are named separately:

Left: C H 3 C H 2 C C H 3. Second carbon from left is doubly bonded to an O. Labeled 2-butanone (methyl ethyl ketone). Middle: cyclohexane bonded to a carbon that is double bonded to an oxygen and single bonded to C H 2 C H 3. Labeled: 1-cyclohexyl-1-propanone (cyclohexyl ethyl ketone). Right: C H 3 C C H 2 C C H 3. Second and fourth carbon double bonded to an oxygen. Labeled 2,4-pentanedione.

When the doubly bonded oxygen is regarded as a substituent along the parent chain or ring, it is called an oxo group, \(=O\),

Left: C H 3 C double bonded to O and single bonded to C H 2 C H 2 C H O. Labeled 4-oxopentanal. Right: cyclohexane single bonded to a C O 2 H on carbon 4 and double bonded to an O on carbon 1. Labeled 4-oxocyclohexanecarboxylic acid.

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."