Kinetics and mechanism of acid hydrolysis of 1-methyl-1-nitroso-3-p-tolylsulfonylguanidine and 1-methyl-1-nitroso-3-benzoylguanidine

Abstract

Kinetics of acid hydrolysis of 1-methyl-1-nitroso-3-p-tolylsulfonylguanidine 2 and of two 1-methyl-1-nitroso-3-benzoylguanidines (4-unsubstituted and 4-chloro) 5 and 6 have been studied. For the acid hydrolysis of 1-methyl-1-nitroso-3-p-tolylsulfonylguanidine 2, the absence of catalysis by thiocyanate ion, and the value of the kinetic solvent isotope effect indicate that either a rate determining proton transfer followed by fast denitrosation or a concerted pathway is involved in the mechanism. In the case of the acid hydrolysis of 1-methyl-1-nitroso-3-benzoylguanidines 5 and 6 it was observed that the protonated form decomposes via two parallel pathways. One involves a slow nucleophilic attack concerted with an intramolecular proton transfer, and the other a slow concerted denitrosation, where a second proton transfer and NO⁺ expulsion are simultaneous.