Lewis acid-assisted detection of nerve agents in water

Abstract

The five-coordinate compound, Salen(^tBu)Al(Ac), prepared in situ from Salen(^tBu)AlBr and NH₄Ac, forms Lewis acid–base adducts in aqueous solution with the G-type nerve agents, Sarin and Soman, and the VX hydrolysis product, ethylmethylphosphonate (EMPA). The resulting compounds, [Salen(^tBu)Al(NA)]⁺[Ac] ⁻ (with NA = Sarin, Soman, and EMPA) are sufficiently stable to be identified by ESI-MS. Molecular ion peaks were detected for every compound with little or no fragmentation. The distinctive MS signatures for the [Salen(^tBu)Al(NA)]⁺ compounds provide a new technique for identifying nerve agents from aqueous solution. The energetics of the displacement of Ac⁻ by the nerve agents to form [Salen(^tBu)Al(NA)]⁺[Ac]⁻ were determined computationally.