On the activation energy for the hydrolysis of bis-(2-chloroethylethyl) sulfide. II

Dilute solutions of mustard, bis-(2-chloroethylethyl) sulfide, hydrolyze to form the chlorohydrin and HCl: the chlorohydrin subsequently hydrolyzes to form the thiodiglycol and another mole of HCl. The kinetics of these reactions constitute consecutive, first-order reactions which past investigators approximated as a single, first-order reaction. In an earlier paper, a non-linear least-squares program was used to refit these data to consecutive, first-order kinetics in order to refine the activation parameters for mustard hydrolysis. It was shown, however, that the early work did not conform to consecutive, first-order reactions, suggesting that dissolution of mustard interfered with the hydrolysis. Only the data of Bartlett and Swain were clearly hydrolysis of mustard: however, rate data were only run at 25°C.This paper reports kinetics of mustard hydrolysis measured in 0.025 mole fraction ethanol-water between 20 and 40°C. Over this temperature range, the enthalpies of activation for mustard and the chlorohydrin are 18.5 and 18.6 kcal mol⁻¹, respectively. These results are similar to enthalpies of activation for other 2-chloroethylalkyl sulfides, but smaller than those reported for mustard hydrolysis in the past.