The transmission of polar effects. Part VIII. Esterification with diazodiphenylmethane and the ionization of ortho-substituted trans-cinnamic, phenoxyacetic, 3-phenylpropionic, cis- and trans-α-phenylcinnamic acids

Abstract

The rate coefficients for the esterification with diazodiphenylmethane in ethanol at 30° and the pKa values at 25° of a number of ortho-substituted trans-cinnamic, phenoxyacetic, 3-phenylpropionic, ortho-, meta-, and para-substituted cis-trans-α-phenylcinnamic acids have been determined. The effects of substitution have been assessed by a Hammett-type correlation. A comparison of the transmission of the polar effects of ortho and meta/para substituents indicates the prime importance of the field effect, augmented where possible by a π-inductive effect. A reversed dipolar substituent field effect has been detected for the cis-ortho-substituted cinnamic acids.