Methylthio Group Migration in the Acid-Catalyzed Hydrolysis of S-Methyl Phenyldiazothioacetate. Kinetics and Mechanism of the Reaction

Article abstract of DOI:10.1021/jo00062a005

The acid-catalyzed hydrolysis of S-methyl phenyldiazothioacetate, C6H5C(=N2)COSCH3, in aqueous solution at 25 deg C was found to occur with the hydronium ion isotope effect k_H(1+)/K_D(1+)=3.08 and to give a Bronsted relation, based on carboxylic acid catalysts, whose exponent is α=0.70.This is taken to mean that the reaction occurs by rate-determining proton transfer to the diazo carbon atom.The principal product of the reaction, however, is α-(methylthio)-α-phenylacetic acid, C6H5CH(SCH3)CO2H, which must be formed by 1,2-shift of the methylthio group.An argument is presented which suggests that this shift is accompanied by a rate acceleration and that it consequently must take place in the rate-determining step of the reaction.