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7.11: Single- or Multiple-Word Names

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    A troublesome point in naming chemical compounds concerns the rules governing when a compound is to be written as a single word (as methylamine) or as two or more words (as methyl chloride). To solve this problem, you must determine whether the principle or parent function is an element or a compounds in its own right; if it is either one, then the name is written as a single word.

    The following examples should help to clarify the system. In each name, the part of the name that denotes the parent compound\(^2\) is italicized:

    Top left: C H 3 C L labeled chloromethane. Top middle: C H 3 N H 2 labeled methylamine. Top right: cyclohexane with a C H O substituent labeled cyclohexanecarbaldehyde. Bottom left: benzene ring with an S that is double bonded to two Os and single bonded to an O H substituent labeled benzenesulfonic acid. Bottom middle: C 6 H 5 L I labeled phenyl lithium. Bottom right: C H 3 M G C H 3 labeled dimethylmagnesium.

    However, if the parent function cannot be constructed as being a real compound, the name is correctly written as two or more words. For example, \(CH_3Cl\) could be named as a chloride, in which case we use two words, methyl chloride, to describe it. A chloride, or any halide, is a class of compound, not a specific compound. To identify a specific halide, the adjective that describes the halide is written as a separate word preceding the class name. Examples follow in which the class name is italicized.\(^3\)

    Left: benzene ring with a C H 2 B R substituent labeled phenylmethyl bromide (benzyl bromide). Middle: C H 3 single bonded to a C that is double bonded to an O  and single bonded to an O H labeled ethanoic acid (acetic acid). Right: Carbon with three C H 3 substituents and one O H substituent labeled tert-butyl alcohol.

    \(^2\)The parent compounds designated here as amine, carbaldehyde, and sulfonic acid are properly ammonia, methanal, and sulfurous acid (\(HSO_3H\)) when no substituent groups are attached.

    \(^3\)These word-separated names sometimes are called radicofunctional names.

    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 7.11: Single- or Multiple-Word Names 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.