Cleavage of VX Simulants by Micellar Iodoso- and Iodoxybenzoate

Abstract

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.

IBX—New Reactions with an Old Reagent

“…[19] IBX (1) is able to oxidize thiols selectively to the corresponding disulfides. [20] It can also be used as a versatile reagent for the cleavage of oximes and tosylhydrazones to the corresponding carbonyl compounds. [21] The first attempts to synthesize chiral reagents derived from IBX have appeared, although the selectivities obtained in the sulfide oxidation are low (up to 16 % ee).…”

Preparation of cationic latexes with different length alkyl groups on their quaternary ammonium ions and their use as supports for IBA catalyst in the hydrolysis of PNPDPP

“…Catalytic efficiencies of their IBA/ latex catalysts on PNPDPP were impressive. Also Moss and coworkers [9][10][11][12][13][14][15][16][17][18] carried out most of the successful work on the hydrolysis of various organophosphate esters with some o-iodosocarboxylates and especially with IBA in the micellar media. In their studies, hexadecyltrimethylammonium chloride (CTACl) was used as the surface active agent.…”

“…Micelles function as the solubilizing medium for organophosphate esters as well as the binding site for IBA. This group intensively investigated IBA mediated hydrolysis of various organophosphate esters especially in the micellar medium of hexadecyltrimethylammonium chloride (CTACl) [9][10][11][12][13][14][15][16][17][18]. The hydrolysis reaction occurs via a nucleophilic attack and the tautomer of 1, namely 1-hydroxy-1,2-benziodoxolin-3-one (2), acts as the superior nucleophile in micellar medium.…”

“…It is well established that this valance tautomeric form (2) is the dominant form in basic conditions [9]. After the discovery of the remarkable catalytic efficiency of IBA, the catalytic activities of it and various iodosyl compounds in micellar media and microemulsions have been investigated for the hydrolysis of various organophosphate esters at slightly basic conditions [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In addition, polymer, silica, and titanium attached IBAs have been prepared as solid decontaminants and used for the same purpose [25][26][27][28].…”

Phosphorolytic Cleavage of Phosphate and Phosphonoformate Diesters by Cetyltrimethylammonium Iodosobenzoate

“…3 Thus, 1 × 10 -4 M IBA in 2.5 mM aqueous (CTA)Cl at pH 8 cleaved 1 × 10 -5 M phosphotriester 2 with k ) 0.074 s -1 , whereas phosphodiester 3 initially appeared not to cleave with IBA at various (CTA)Cl concentrations under similar conditions. 3,8 Presumably, attack of the anionic IBA is inhibited at the phosphorus center of the anionic O-P-O triad of BNPP.Recently we reported that cetyltrimethylammonium iodosobenzoate 9 (4, (CTA)IBA) is 20-30% more reactive than a 1:1 (CTA)Cl-IBA blend in the micellar hydrolyses of paraoxon and parathion. 6 In holomicellar (CTA)IBA, where there are no chloride ions to compete for the cationic CTA binding sites, the reactive IBA anions may bind more strongly at the CTA cationic sites, affording more efficient reaction with the hydrophobically bound (neutral) substrate.…”