Catalytic Rearrangement of O, S-Dialkyl Dithiocarbonates to S, S-Dialkyl Dithiocarbonates. III. The Reaction Mechanism

Abstract

An experiment was carried out to confirm the reaction mechanism involving the formation of a carbonium ion which had been postulated previously for the catalytic rearrangement of O, S-dialkyl dithiocarbonates to S, S-dialkyl dithiocarbonates with Lewis acid. Optically active S-methyl O-2-octyl dithiocarbonate underwent rearrangement catalytically to S-methyl S-2-octyl dithiocarbonate with racemization. Kinetic study of the catalytic rearrangement of O-butyl S-methyl dithiocarbonate showed that the reaction rate was proportional to the concentrations of both O, S-dialkyl dithiocarbonate and the catalyst. The rate constants of O-alkyl S-methyl dithiocarbonates (ROCSSCH₃) increased in the order of alkyl groups (R) of iso-Pr>Me≈Et≈n-Pr≈n-Bu. These chemical and kinetic observations support the postulated carbonium ion mechanism.