Solvent Effects on the Heterogeneous Adsorption and Reactions of (2-Chloroethyl)ethyl Sulfide on Nanocrystalline Magnesium Oxide

Abstract

The noncatalytic destructive adsorption of (2-chloroethyl)ethyl sulfide (2-CEES), a mimic of bis(2-chloroethyl) sulfide (“HD” or Mustard Gas), on nanocrystalline magnesium oxide (AP-MgO) was studied in several solvents from pentane to methanol. The decomposition products formed in these reactions were vinylethyl sulfide and (2-hydroxyethyl)ethyl sulfide. Reactions in pentane allowed the highest reaction rates, while tetrahydrofuran (THF) and methanol gave results quite different from those for the hydrocarbon solvent. Reactions in methanol yielded (methoxyethyl)ethyl sulfide and not the vinylethyl sulfide and (2-hydroxyethyl)ethyl sulfide compounds. These studies showed that the MgO-2-CEES reaction chemistry is significantly affected by the solvent present and can be enhanced by choice of solvent and the addition of small amounts of water. Interestingly, the least polar, least reactive solvent (pentane) allowed the most rapid 2-CEES reactions, indicating that the solvent simply aided material transfer to the reactive surface sites without blocking these sites. Rate changes upon water addition, coupled with FTIR studies, indicate that isolated surface OH groups are important reactive sites. These results indicate that the use of certain “inert” solvents greatly aids material transfer, and thereby the reaction rates of the sorbent with the toxin are significantly enhanced.