Oxidation, Destruction, and Persistence of Multilayer Dimethyl Methylphosphonate Films during Exposure to O(³P) Atomic Oxygen

Abstract

We present work detailing the oxidative reactivity of the nerve agent simulant dimethyl methylphosphonate (DMMP) with atomic oxygen using time-resolved in situ reflection−absorption infrared spectroscopy (RAIRS) and Xray photoelectron spectroscopy (XPS). When exposed to a supersonic beam containing O( 3 P) with average translational energy of 0.12 eV, thermally annealed DMMP films (less than 50 layers) on single-crystal Au( 111) are observed to react, likely via hydrogen abstraction, and followed by various secondary reactions with resultant hydroxyl and DMMP-derived radicals. This reaction is accompanied by the appearance of hydrogen bonding interactions with the DMMP phosphoryl (PO) groups on the film surface, and it is also observed to result in both a loss of carbon and an uptake of oxygen by the film. These trends, when considered with the additional thermal stability of reaction products left on the surface, suggest that the mechanism entails reaction with DMMP methyl groups and the formation of various polymeric species; the presence of these polymers hinders continuous, effective destruction for films thicker than roughly ten layers. This work has specific implications for the implementation of plasma-based and oxidative decontamination methods based upon an improved fundamental understanding of the chemistry of the important class of phosphoryl containing molecules.

Rapid Laser-Induced Temperature Jump Decomposition of the Nerve Agent Simulant Diisopropyl Methylphosphonate under Atmospheric Conditions

“…In addition to experimental and theoretical work on the thermal decomposition and combustion of these compounds, 11,17,19−21 this work is an extension of previous studies examining oxidative 22,23 and laser destruction 24 of adsorbed chemical nerve agent simulants under ultrahigh vacuum conditions. The oxidative destruction of DIMP and dimethyl methylphosphonate (DMMP) progresses at similar rates and yields oxygen-and carbonyl-containing oligomeric product species.…”

“…In addition to experimental and theoretical work on the thermal decomposition and combustion of these compounds, ,,− this work is an extension of previous studies examining oxidative , and laser destruction of adsorbed chemical nerve agent simulants under ultrahigh vacuum conditions. The oxidative destruction of DIMP and dimethyl methylphosphonate (DMMP) progresses at similar rates and yields oxygen- and carbonyl-containing oligomeric product species. , Laser desorption and destruction studies of a number of Sarin simulants, (DIMP, DMMP, and diethyl ethylphosphonate), demonstrated lower temperature thresholds for destruction of simulants with relatively larger phosphonate side chains . On the basis of these results, we again expect that the majority of gas-phase products in this study will include a variety of 1, 2, and 3-carbon products generated from the DIMP isopropyl group, with possible incorporation of atmospheric oxygen.…”

“…The oxidative destruction of DIMP and dimethyl methylphosphonate (DMMP) progresses at similar rates and yields oxygen-and carbonyl-containing oligomeric product species. 22,23 Laser desorption and destruction studies of a number of Sarin simulants, (DIMP, DMMP, and diethyl ethylphosphonate), demonstrated lower temperature thresholds for destruction of simulants with relatively larger phosphonate side chains. 24 On the basis of these results, we again expect that the majority of gas-phase products in this study will include a variety of 1, 2, and 3-carbon products generated from the DIMP isopropyl group, with possible incorporation of atmospheric oxygen.…”

A Theoretical and Mass Spectrometry Study of Dimethyl Methylphosphonate: New Isomers and Cation Decay Channels in an Intense Femtosecond Laser Field

“…Dimethyl methylphosphonate (DMMP, PO 3 (CH 3 ) 3 ) is used in practical applications as a flame retardant. , As a simulant for toxic organophosphorus nerve agents such as VX, sarin, and soman, study of DMMP is also useful to develop sensors for chemical warfare agents and catalysts that drive their decomposition . Materials including alkanethiolate monolayers, carbon nanotubes, and metal oxides have recently been developed for DMMP sensing applications. − The study of reactions and decomposition of DMMP on the surfaces of various metal oxides and oxide supported catalysts such as metal nanoparticles, both at room and elevated temperatures, has been an active area of research for over 2 decades. − Additionally, multiple studies have demonstrated oxidative − and plasma-mediated − decomposition of DMMP. To assist in interpreting the decomposition mechanisms of DMMP on various heterogeneous catalysts, a number of computational studies of the electronic structure and gas phase unimolecular decomposition pathways of DMMP have recently been performed. − …”

Oxidative Destruction of Multilayer Diisopropyl Methylphosphonate Films by O(3P) Atomic Oxygen

“…Most of the experimental details described here are identical to those used in a recent paper on the analogous reaction between O­( 3 P) and DMMP films . One difference, however, is in the method for simulant film deposition.…”