No abstract

No abstract

0,s-Dialkyl phenylphosphonothioates (5a-d) are good simulants for the nerve agent VX in nucleophilic substitution reactions. Hydrolyses of 5a-d in 0.1 M aqueous NaOH occur with half-lives of 4-18 min and with the formation ofboth P-S and P-0 cleavage products, 6a-d and 7a-d, respectively. Reactions of these substrates with o-iodosobenzoate (IBA), however, are chemospecific at P-S. For example, in 0.05 M micellar cetyltrimethylammonium chloride (CTAC1) at pH 9.5 (pD 9.9) in DzO, 0.063 M IBA cleaved 0.02 M 5a (to 6a) with K = 0.115 min-l, t112 -6 min. The second-order rate constant for this reaction in 0.1 M CTACl solution was -1.9 M-l min-l.The destruction of phosphorus-based nerve agents under battlefield ("decontamination") or treaty-mandated stockpile ("demilitarization") conditions continues to be a matter of urgent ~o n c e r n .~-~~ For fluorophosphonate toxins such as soman (GD), 1, and sarin (GB), 2, mildly basic aqueous micellar solutions ofo-iodosobenzoate (315 or its derivatives effectively catalyze rapid and efficient hydrolysis.6 In contrast, the phosphonothioate agent, VX(4), was reported

Several parameters of the Novichok nerve agents A230, A232 and A234 were determined. Hydrolysis rates were approximately one to three orders of magnitude slower than G-type nerve agents and approximately zero to two orders of magnitude slower than V-type nerve agents. A230 was the most labile Novichok compound followed by A232 then A234. Activation energies (E a ) and frequency factors (A) were determined for all three compounds. The organophosphorus acid anhydrolase (OPAA) enzyme had catalytic efficiencies on the Novichok compounds ranging between 10 4 and 10 5 M À1 min À1 with the highest k cat /K m value for A230, then A232 and lastly, A234.

No abstract