Photocatalytic destruction of a thiosulfonate

Organic sulfur compounds have received considerable attention in photocatalysis research due to their increased environmental threat and potentiality to discover novel organic synthesis routes. Experimental and quantum chemical consideration of photocatalytic and photochemical transformations in acetonitrile of CH₃C₆H₄S(O₂)SCH ₂CH₂N(iPr)₂ (diisopropylaminoethyl 4-methylbenzenethiosulfonate, DAMT), an imitant of chemical agent VX with close structural properties and ionization energy were presented. Diisopropylaminoethyl disulfide and 4-methylbenzene-sulfonic acid were detected as major products of photocatalytic and photochemical degradation. Photocatalytic degradation stopped at about 60% DAMT conversion due to acidification of the system. Photochemical degradation proceeded slower but to a higher conversion since DAMT protonation did not stop photolysis completely. DAMT^.+ formed at the first step of photocatalytic degradation, then it split into CH₃C₆H₄SO₂ and SCH₂CH₂N⁺(iPr)₂. The former fragment transformed into sulfonic acid and the latter decomposed into SCH₂ and CH₂N⁺(iPr)₂ in the absence of TiO₂, the route observed in MS. However, it was stable in adsorbed state on the TiO₂ surface and after reduction with photogenerated electron recombined to produce the disulfide product. The results suggested that photocatalytic and photolytic detoxification of VX is possible provided conditions are adjusted for its complete conversion.