Issue 0, 1968

The separation of polar and steric effects. Part VII. The kinetics of the acid-catalysed esterification of substituted phenylacetic acids by methanol

Abstract

Rate coefficients have been determined for the acid-catalysed esterification by methanol at 40° of phenylacetic acid and various ortho- and meta-substituted phenylacetic acids (substituents: o-F, o- or m-Cl, o-Br, o-l, o- or m-Me, o-Et, o-Pri, or m-NO2). The Hammett ρ-value is –0·31, but the reaction of m-methylphenylacetic acid does not conform with the Hammett equation.

Phenylacetic acid reacts ca. 100 times more rapidly than benzoic acid; the factors underlying this are discussed. Taft Es values are tabulated for ortho-substituents in benzoic and phenylacetic acid. With ortho-alkyl groups the Es values are numerically smaller for the phenylacetic than for the benzoic acids, but the opposite applies for ortho-halogeno-substituents. We suggest that ortho-halogeno-substituents in phenylacetic acid are more heavily solvated than when they are in benzoic acid, and that therefore they behave as if they are larger.

Article information

Article type
Paper

J. Chem. Soc. B, 1968, 164-167

The separation of polar and steric effects. Part VII. The kinetics of the acid-catalysed esterification of substituted phenylacetic acids by methanol

N. B. Chapman, M. G. Rodgers and J. Shorter, J. Chem. Soc. B, 1968, 164 DOI: 10.1039/J29680000164

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