Bond Scission in Sulfur Compounds. Part X. The Hydrazinolysis of Methyl p-Nitrophenyl Sulfate

Abstract

Reaction of methyl p-nitrophenyl sulfate with the hydrazine – hydrazine hydrochloride system in methanol gives rise to different types of behavior depending on the state of ionization of the reagent. For the H2NNH2/H2NNH3+ combination the observed reaction is conversion of methyl p-nitrophenyl sulfate to p-nitrophenyl sulfate ion (alkyl–oxygen scission). For the H2NNH3+/+H3NNH3+ combination, or with +H3NNH3+ alone, one observes the consecutive processes methyl p-nitrophenyl sulfate → p-nitrophenyl sulfate ion → p-nitrophenol (alkyl–oxygen followed by sulphur–oxygen scission). For the alkyl–oxygen scission process, i.e. nucleophilic displacement on the alkyl carbon, the observed pseudo first-order rate constant is given by the contributions of several nucleophilic species; [Formula: see text] A method for the dissection of kobs into the constituent terms is given. The sulphur–oxygen scission process is an acid catalyzed reaction and the measured kinetic data have been utilized for the derivation of the pKa of +H3NNH3+ in methanol. Rate data for the conversion of sodium p-nitrophenyl sulfate to p-nitrophenol in methanol containing HCl have also been determined in this connection.