The rates of reaction of methyl trifluoromethanesulphonate with a number of cyclic and open-chain disulphides have been studied at various temperatures. The main products of the reactions have been identified as the corresponding methylsulphonium salts. The difference in reactivity between the fivemembered and other disulphides arises from a combination of both enthalpy and entropy effects.

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The positions of bond-fission in the hydrolyses of ethylene sulphite, propylene sulphite, meso-2 : 3-butylene sulphite, tetramethylethylene sulphite, trimethylene sulphite, and 1 : 3-butylene sulphite have been determined isotopically under acidic and alkaline conditions. Sulphur-oxygen bond-fission occurs in all the examples studied. It has been shown, for ethylene and for trimethylene sulphite, that the organic sulphite, originally isotopically normal, is still normal when recovered after partial hydrolysis in isotopically enriched water under either acidic or alkaline conditions.GARNER and LUCAS showed that the formation, followed by the acid-or alkali-catalysed hydrolysis, of 2 : 3-butylene sulphite proceeded without change in the optical activity of the butane-2 : 3-diol used as starting material. They concluded that these hydrolyses proceed with sulphur-oxygen bond-fission. Foster, Hancock, and Overend have studied the hydrolyses of the cyclic sulphites of the cyclohexane-1 : 2-diols. The transisomer gave the trans-diol; the cis-isomer gave the cis-diol in acidic solution, and mainly the trans-with some cis-diol, in alkaline solution. From this they concluded that some Garner and Lucas,

The acid-catalysed hydrolyses of some N-(para-substituted pheny1)propane-I ,3-sultams have been studied in aqueous acidic solutions. The rate maxima observed are shown to be consistent with an A-2 mechanism in which extensive protonation of the substrate occurs. Values of pK,,+ for the sultams have been determined.Whilst the acid-catalysed hydrolysis of sulfonamides has been studied in some detail because of its relevance to the Hinsberg method for the separation of amines, very few studies of the hydrolyses of sultams (the corresponding cyclic sulfonamides) have been recorded.' Erman and Kretschmar reported that a number of five-membered N-alkyl sultams undergo hydrolysis in methanolic HCl or HBr or in glacial acetic acid.2 They suggested that acid catalysed cleavage of the ring proceeds via an A-1 mechanism by analogy to the mechanism proposed earlier for the acid-catalysed hydrolysis of sulfonamides3 although Klamann and his co-workers subsequently changed this view.4 In order to clarify the situation for the hydrolysis of sultams, we now report a detailed study of the protonation behaviour and kinetics of hydrolysis of a series of fivemembered N-arylpropane-1,3-sultams 1 in aqueous solutions of mineral acids.

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in the cases of ethylene and trimethylene sulphites, which serve as the simplest examples of 1 : 2-and of 1 : 3-sulphites. EXPERIMENTALThe properties of the cyclic sulphites are recorded in Part 1.l The acids were of Analytical Reagent quality. Their concentrations were determined in the reaction mixtures by titration with standard alkali. Sodium chloride and sodium bromide were dried a t 120". Sodium perchlorate was dried for 4 days a t 120"; it was free from halide. Sodium toluene-p-sulphonate was a commercial recrystallised specimen. Tetraethylammonium perchlorate was prepared from tetraethylammonium hydroxide by neutralisation with perchloric acid. The precipitate was washed with water until the washings were neutral, then dried at 100'.The conversion of organic sulphite into sulphur dioxide was determined a t intervals by breaking samples under excess of standard iodine solution, which was then back-titrated with sodium thiosulphate. The following exemplifies a typical kinetic run, for 0.036hl-ethylene sulphiteThe rates of hydrolysis were determined by a conventional sealed-tube method. Time (min.) .