Abstract
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 language | English |
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Pages (from-to) | 180-189 |
Number of pages | 9 |
Journal | Journal of Physical Organic Chemistry |
Volume | 20 |
Issue number | 3 |
DOIs | |
Publication status | Published - Mar 2007 |
Keywords
- Acid chlorides
- Aliphatic carboxylic acids
- Esters
- Hydrolysis
- Kinetics
- Reaction mechanism
- Steric and electronic effects