Transmission of substituent effects via 1,2,4-triazole ring residue

Abstract

The ionization constants of a series of 5-phenyl-3-substituted phenyl-1,2,4-triazole- 3-carboxylic acids (<strong>2a-j</strong>), prepared by the base catalysed rearrangement of 2-phenyl-4-arylazo-5-oxazolones (<strong>1a-j</strong>), and the rate of alkaline hydrolysis of the corresponding methyl esters (<strong>3a-j</strong>) have been measured in 80% (v/v) ethanol at 30&deg;C and ionic strength of 0.1. Both the equilibrium and rate constants have been correlated by Hammett equation, the values of the reaction constant p being 0.45 and 0.24 respectively. A comparison of presently reported values with those reported in literature for ionization of benzoic acids and alkaline hydrolysis of methyl benzoates indicates that the 1,3-(1,3,4-triazole) ring residue is 39% and 10% efficient in transmitting substituent electronic effects in 2 and 3 respectively.