Reactions of VX, GD, and HD with nanosize CaO: Autocatalytic dehydrohalogenation of HD

Room-temperature reactions of the chemical warfare agents VX, GD, and HD wi th nanosize CaO (AP-CaO), and HD with commercial CaO have been studied usin g solid-state MAS NMR. VX and GD hydrolyze to yield surface-bound complexes of nontoxic ethyl methylphosphonate and pinacolyl methylphosphonate, respe ctively. The kinetics are characterized by an initial fast reaction followe d 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-Ca O (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 wh ich 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, wh ich apparently reside as surface alkoxides. Such kinetic behavior was not e vident for the common mustard simulant 2-chloroethyl ethyl sulfide (CEES) o n partially hydrated AP-CaO, which exhibited only the typical fast/diffusio n-limited reaction.