Solvolysis of dimethylsulphamoyl chloride in water and aqueous acetone

Abstract

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 k_H2O/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 k_obsvs.Y with a slope (m) of 0·69. From the present results, and from comparison with m and k_OH/k₀ values for other sulphonyl chlorides, it is concluded that the reaction is S_N2 with a loose transition-state with some ionic character.