Study on the Kinetics and Transformation Products of Sulfur Mustard Sulfoxide and Sulfur Mustard Sulfone in Various Reaction Media

Considering postulates of the Chemical Weapons Convention, this article is an attempt to improve the decontamination methods of mustard gas (HD) and studying its products of decontamination. It is widely known that mustard gas sulfoxide (HDO; O═S(CH₂CH₂Cl)₂) and sulfone (HDO₂; O₂═S(CH₂CH₂Cl)₂) undergo further transformations to another compounds, but so far kinetics of these processes have not yet been investigated neither carefully nor thoroughly. This study is focused on determination of kinetics and mechanisms of transformation of HD oxidation products. The primary objective of this study is to assess the impact of selected factors on the kinetics of the HCl elimination reaction and to determine the conditions in which cyclization reactions of divinyl sulfoxide and sulfone proceed. The HDO and HDO₂ decay kinetics were monitored in an aqueous solution of the desired pH. The rate of HCl elimination from HDO and HDO₂ is strongly dependent on pH. For example, with pH increasing from 9 to 12 the rate of HCl elimination from HDO increased over 1200 times. In solutions of pH 9, HDO loses hydrogen chloride at approximately 100 times slower compared to HDO₂, and the difference is reduced with increasing pH. In pH 12 solutions, the rate of hydrogen chloride loss from HDO₂ is only 20 times higher than the HCl loss from HDO. Divinyl sulfoxide and sulfone undergo a further transformation in a strongly alkaline environment, leading to cyclization and formation of 1,4‐thioxane sulfoxide and sulfone, respectively. Elimination of HCl from HDO and HDO₂ goes with a rapidly increasing rate with increasing pH if alkalinity of the reaction medium is relatively very high (the range of pH 9–12). Furthermore, the conversion of divinyl sulfone and sulfoxide to sulfoxide and sulfone thioxane, respectively, occurs at a measurable rate when the pH of the solution is in the range of 12–14.