Methoxymethyl phenyl sulfoxide 1 undergoes acid-catalyzed hydrolysis to give S-phenyl benzenethiosulfinate 5, which is formed rapidly from a primary product, benzenesulfenic acid 3. Formation of 5 follows pseudo-first-order kinetics. Rate constants obtained spectrophotometrically in perchloric acid show that the reaction is dependent on the protonated substrate with the Bunnett–Olsen φ=−0.15. Rate constants for the loss of optical activity of the enantiomeric 1 measured in 80 vol% aqueous dioxane are identical with those obtained spectrophotometrically for the formation of 5. Racemization of the substrate does not take place more rapidly than the fragmentation. The reaction is accelerated by chloride and bromide ions. The halide reaction is first order in acid concentration.

This paper is dedicated to Professor Arthur N . Bourns TADASHI OKUYAMA, MASAYOSHI TOYODA, and TAKAYUKI FUENO. Can. J. Chem. 64, 11 16 (1986).Hydrolyses of Zethylidene-( l b ) , 2-isopropylidene-( l c ) , and 2-benzylidene-l,3-dithiolane ( I d ) were kinetically investigated in aqueous solution. All the individual rate constants involved in this three-step reaction were evaluated. Initial carbon protonation is only partially reversible (k2/k-1 = 1.33,0.68, and 1.02 for l b , l c , and Id, respectively) at higher pH, while the protonation becomes completely reversible below pH 2 where the thud step is rate determining. Complete H-D isotopeexchange at the P-carbon of l b and Id was observed in deuterium media before appreciable hydrolysis took place. It was demonstrated that reversion from the tetrahedral intermediate 3 to 1 occurs extensively during the reaction in the latter acidity range. Relative stabilities and reactivities of the olefinic substrates 1 are discussed. que, au cours de la rCaction, la transformation de l'intenntdiaire tCtraidrique 3 en 1 ne se produit que dans le dernier intervalle de pH. On discute des stabilitCs et des rtactivitts relatives des substrats olCfiniques 1.[Traduit par la revue]

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