SOLVOLYSIS OF DIMETHYLSULPHAMOYL CHLORIDE IN WATER AND AQUEOUS ACETONE

The solvolysis of dimethylsulphamoyl chloride in aqueous acetone (0-80% acetone) has been studied. The reaction is independent of pH in the range 3-11. At 25° the observed rate constant in water is 3.98 × 10-3 sec.-1 and the activation parameters ΔH‡ and ΔS‡ are 16.6 kcal. mole and -22.0 cal. mole-1 deg. -1 respectively. The solvent-isotope effect kH2O/k D2O is 1.33. The reaction is free from common-ion and salt effects. In the presence of sodium azide the observed rate increases linearly with azide concentration. The solvolysis reaction in aqueous acetone correlates well with the Winstein Y values, and gives a linear plot of log kobs vs. Y with a slope (m) of 0.69. From the present results, and from comparison with m and kOH/k0 values for other sulphonyl chlorides, it is concluded that the reaction is SN2 with a loose transition-state with some ionic character.