Effects of mixed H 2 O‐CH 3 CN solvents on the rate of hydrazinolysis of N ‐phenylphthalimide: Spectral and kinetic evidence for the occurrence of N ‐aminophthalimide on the reaction path

Kinetic study on the cleavage of N ‐phenylphthalimide (NPhPT) in the presence of 0.05 M NH 2 NH 2 and mixed H 2 O‐CH 3 CN solvents reveals the occurrence of reaction schemewhere A, B, C, C 1 , An, E, and F represent NPhPT, o ‐CO − 2 C 6 H 4 CONHC 6 H 5 , o ‐CONHNH 2 C 6 H 4 ‐ CONHC 6 H 5 , N ‐aminophthalimide, aniline, o ‐CO − 2 C 6 H 4 CONHNH 2 , and o ‐CONHNH 2 C 6 H 4 ‐CONHNH 2 , respectively. But, in the presence of either nonbuffered ⩾0.20 M NH 2 NH 2 hydrazine buffer of pH ∼7.30–8.26 with total buffer concentration ([Buf] T ) of >0.02 M, further conversion of F to 2,3‐dihydrophthalazine‐1,4‐dione (DHPD) has been detected depending upon the length of the reaction time ( t ), the values of [Buf] T , and pH. It has been shown that the rate of conversion of C 1 to F is much faster than that of C to C 1 which is much faster than that of F to DHPD. The reaction step A → C involves general base (GB) catalysis, while step C → C 1 seems to involve specific base–general acid (GA) and GB‐GB catalysis. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 147–161, 2005