Kinetic Evidence for the Occurence of a Stepwise Mechanism in Hydrazinolysis of Phthalimide

Article abstract of DOI:10.1021/jo00119a035

The apparent second-order rate constants, k_napp, for the reaction of hydrazine with phthalimide at a constant pH follow the empirical relationship k_napp = A_1T/(1 + A_2T), where _T represents the total hydrazine buffer concentration.The nonlinear variation of k_napp against _T is attributed to the change in the rate-determining step with change in _T at a constant pH, and this provides evidence for the existence of an intermediate on the reaction path.The cyclization of o-(aminocarbamoyl)benzamide to 2,3-dihydrophthalazine-1,4-dione involves N-aminophthalimide as the intermediate.