Solvolysis of sulphonyl halides. VII. Hydrolysis of some aromatic sulphonyl chlorides in aqueous dioxan

Abstract

The rates of reaction and the parameters of activation have been determined for the hydrolysis of 4-nitro-, 3-nitro-, 4-bromo-, 4- methoxy-, 4-methyl- and unsubstituted benzenesulphonyl chlorides m aqueous dioxan containing mole fractions of water between 0.9 and 1.00. Further evidence is also found for Vizgert's hypothesis that 2,4,6- trimethylbenzenesulphonyl chloride hydrolyses by the S_N1 mechanism. In all other cases the inversion of the effects of substituents which occurs as the water content of the solvent is decreased, the passage of the rate through a maximum in certain cases, and the failure of the Hammett free energy correlation can be accounted for in terms of 8,2 type mechanisms for hydrolysis in which both bond-making and bond-breaking processes are of importance but are differently biased by the various substituents.