Cleavage of VX Simulants by Micellar Iodoso- and Iodoxybenzoate

O,S-Diethyl phenylphosphonothioate (5) and S-phenyl (9) and S-ethyl diphenylthiophosphinate (10) were efficiently cleaved by 3-fold excess o-iodosobenzoate (IBA) in aqueous micellar cetyltrimethylammonium chloride solutions at pH 9.5. The maximum observed rate constants (monitored by HPLC aliquot procedures) were 1.09 × 10-3 s-1 for 5 and 6.0 × 10-3 s-1 for 10 with 0.06 M IBA at 25 °C. 9 cleaved too rapidly to follow by the aliquot method. With equimolar quantities of 5 and IBA, cleavage was slower and incomplete because of the reduction of the IBA to iodobenzoate by the EtSH liberated in the cleavage step. Mixtures of IBA and o-iodoxybenzoate (IBX) efficiently cleaved 5, even though IBX was not reactive toward 5, because the IBX competitively oxidized the EtSH, mitigating its reaction with IBA, while simultaneously affording additional IBA as the IBX was reduced. Studies of IBA and IBX redox reactions with EtSH are also included.