Structure and reactivity in the hydrolyses of aliphatic carboxylic acid esters and chlorides

Andrew C. Regan, C. Ian F Watt

    Research output: Contribution to journalArticlepeer-review


    For hexanoic acid and its seven isomers, relative rates have been determined for acid catalysed esterification with methanol, and compared with those for saponification of the methyl esters. A good correlation between logarithms of relative rates for the two reactions is obtained, and it is suggested that the eight isomers provide a test set of compounds in which steric effects alone act on reactivity at the acyl carbon. A full set of steric parameters (Es′ values) are presented. Rates of solvolyses of the acid chlorides- of the isomers have been determined conductometrically in 3:1 wt:wt acetonitrile water. Logarithms of relative rates show a poor correlation with Es′, and, taking into account the solvent dependence of the rates, the pattern excludes both rate-limiting formation of a tetrahedral intermediate and rate-limiting dissociation of chloride to form acylium ions. The remaining possibilities, a concerted process (ANDN‡) and rapid reversible formation of a hydrate followed by rate-limiting dissociation of chloride (AN + DN‡,) are considered. Copyright © 2007 John Wiley & Sons, Ltd.
    Original languageEnglish
    Pages (from-to)180-189
    Number of pages9
    JournalJournal of Physical Organic Chemistry
    Issue number3
    Publication statusPublished - Mar 2007


    • Acid chlorides
    • Aliphatic carboxylic acids
    • Esters
    • Hydrolysis
    • Kinetics
    • Reaction mechanism
    • Steric and electronic effects


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