Reactions of VX, GD, and HD with Nanosize CaO: Autocatalytic Dehydrohalogenation of HD

Abstract

Room-temperature reactions of the chemical warfare agents VX, GD, and HD with nanosize CaO (AP-CaO), and HD with commercial CaO have been studied using solid-state MAS NMR. VX and GD hydrolyze to yield surface-bound complexes of nontoxic ethyl methylphosphonate and pinacolyl methylphosphonate, respectively. The kinetics are characterized by an initial fast reaction followed by a slower, diffusion-limited reaction. Similar behavior is observed for HD on either dried or hydrated AP-CaO and CaO. On partially hydrated AP-CaO (but not CaO), a rather fast steady-state elimination of HCl occurs after an induction period. This behavior is attributed to acid-catalyzed surface reconstruction (to regenerate fresh surface) and the formation of CaCl2, which is known to be more reactive than CaO. The product distribution for HD is about 80% divinyl sulfide and 20% thiodiglycol and/or sulfonium ions, which apparently reside as surface alkoxides. Such kinetic behavior was not evident for the common mustard simulant 2-chloroethyl ethyl sulfide (CEES) on partially hydrated AP-CaO, which exhibited only the typical fast/diffusion-limited reaction.