KINETICS OF CYCLIZATION OF METHYL S-(2,4,6-TRINITROPHENYL)-MERCAPTOACETATE TO ETHOXYCARBONYL-5,7-DINITRO-BENZO[D]THIAZOL-3-OXIDE

The cyclization kinetics of methyl S-(2,4,6-trinitrophenyl)mercaptoace tate to methoxycarbony]-5,7-dinitrobenzo[d]thiazol-3-oxide have been s tudied in acetate, methoxyacetate or N-methplmorpholine buffers. In th e acetate and methoxyacetate buffers, the cyclization obeys the rate e quation v = [SH](k(MeO)'[CH3O-] + k(B)'[B-] + k(B,MeO)'[B-][CH3O-]) an d goes by two reaction paths differing in the order of their reaction steps, the splitting off of the proton from C-H group being the rate-l imiting step in either path. In the N-methylmorpholine buffers, increa sing concentration of the base results in gradual decrease of reaction order in the base and change in the rate-limiting step of cyclization . Methyl S-(2,4-dinitrophenyl)mercaptoacetate undergoes cyclization ne ither in the given buffers nor in methoxide solution.