Theoretical studies on phenyl group migration of protonated 1,2-diphenyl hydrazines

Phenyl group migration within protonated 1,2-diphenyl hydrazines has been s tudied theoretically using the semi-empirical AMI method. This reaction pro ceeds through a 3-membered cyclic transition state and requires high activa tion energy. In the reactant, there was no resonance stabilization for the moving Z-ring, however, resonance stabilization between two nitrogen atoms and the Z-ring was achieved at the transition state. The Hammett rho z(+) v alues are large due to the direct involvement of the Z-ring in the reaction , and the development of a negative charge on the reaction center gives the m a positive value. In the case of the non-moving ring, rho(Y) values are s mall and negative owing to the smaller positive charge increase in the reac tion center. The cross-interaction constant, rho(YZ), was Obtained from the activation enthalpies, using the multiple linear regression method, and th e interaction between two substituents, Y and Z, is examined.