Acid-Catalyzed Cleavage of Methoxymethyl Phenyl Sulfoxide. Solvent Effects and Mode of Bond Cleavage

Abstract

Abstract Rate constants for the acid-catalyzed hydrolysis of methoxymethyl phenyl sulfoxide increase with increasing composition of dioxane in aqueous dioxane solution in contrast to the isomeric sulfenate which is strongly decelerated by added dioxane fraction (up to 90 vol%). The isotope distribution in the products obtained from the [18O]-sulfoxide was examined in 95 vol% aqueous dioxane. About 90% of the 18O was retained in the product S-phenyl benzenethiosulfinate from the reaction with hydrochloric and hydrobromic acid while only 50–60% of the 18O was found in the thiosulfinate from the reaction with perchloric acid. A plausible reaction mechanism involving ligand coupling within a hypervalent intermediate is proposed for the partial loss of the 18O label in the latter reaction.