Mononuclear heterocyclic rearrangements. Part 2. Substituent effects on the rate of rearrangement of some arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole, at pS+ 3.80

Abstract

The rates of the mononuclear heterocyclic rearrangement of some meta- and para-substituted phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (Ia–m) into 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazole (IIa–m) have been measured in dioxan–water (1 : 1 v/v) at pS⁺ 3.80 and at various temperatures; the relevant activation parameters have also been determined. The results obtained, analysing the kinetic data by means of the Ingold–Yukawa–Tsuno equation (ρ– 1.31, r⁺ 0.10, r^– 0.25, correlation coefficient 0.9996), show that the reaction rate is moderately affected by the nature of the substituents present in the aryl fragments of phenylhydrazone and are consistent with an internal nucleophilic displacement by nitrogen on nitrogen.