Investigation of electronic effects in the pyridine and pyridine N-oxide rings. Part 2. Reaction of substituted pyridine- and N-oxylpyridine-carboxylic acids with diazodiphenylmethane

Abstract

The reactivity of a series of substituted pyridine- and N-oxylpyridine-carboxylic acids with diazodiphenylmethane has been investigated and the empirical Hammett treatment applied to a study of substituent effects. In general, satisfactory additivity of substituent effects was obtained, and it was possible to correlate with the same regression line the rate constants for both investigated series. The calculated reaction constant (ρ 0·818) differs from that for substituted benzoic acids, reflecting the same attenuating effect observed in the hydrolysis of substituted pyridine carboxylates. A satisfactory correlation for the ρ_DDM–ρ_hydr relationship was obtained with literature data for the hydrolysis of corresponding substituted methyl pyridinecarboxylates.