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

Abstract

We present work detailing the destruction of the nerve agent simulant diisopropyl methylphosphonate (DIMP) via rapid laser heating under atmospheric conditions. Following Nd:YAG laser ablation of liquid DIMP deposited on a graphite substrate, both parent and product fragments are transmitted via capillary from an atmospheric chamber to a vacuum chamber containing a high-resolution mass spectrometer. This allows for real-time measurements of product distributions under a variety of temperature and atmospheric conditions. Ex situ Fourier transform infrared (FTIR) spectroscopy analysis of the same chamber contents provides complementary information about product identities and fragmentation pathways. Results demonstrate that product distributions depend on heating rate, surface temperature, and atmospheric oxygen content. In the destruction of the DIMP, the relative yields of alkene products depends significantly on laser power; smaller products are relatively more abundant at higher ablation temperatures. We also show that in the absence of atmospheric oxygen, the concentration of oxygenated products decreases sharply relative to alkene and alkane products. This suggests that under high-temperature conditions, atmospheric oxygen is incorporated directly into the products of the fragmented simulant. This project extends significantly our understanding of the fundamental chemistry of these dangerous compounds under atmospheric and rapidly changing thermal conditions. The results have critical implications for the development of effective chemical warfare agent decontamination and destruction strategies.

High-Temperature Decomposition of Diisopropyl Methylphosphonate on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

“…In Figure 5 Free Energy Profiles. The propene end-products predicted by our BOMD simulations corroborates previous experiments on DIMP, which include thermal decomposition studies, 55,56 pyrolysis and combustion in nitrogen/oxygen-rich environments, 57 and microwave 28 and laser-induced 30 decomposition under inert environments. Collectively, all of these prior experimental studies detected propene as one of the main byproducts of DIMP decomposition, which further supports our BOMD predictions.…”

“…DIMP is the only surrogate with the same isopropyl (OC 3 H 7 ) group found in sarin gas (the only structural difference between sarin and DIMP is the substitution of a fluorine for an isopropyl group in the former). Several techniques have also been used to probe DIMP decomposition, including microwave discharge approaches, 28 pyrolysis on porous substrates, 29 laser heating, 30 and thermal decomposition at 700−800 K. 31 and rates of thermal decomposition of DIMP. 32 In this work, we utilize large-scale ab initio molecular dynamics simulations to probe the adsorption dynamics and time scales of DIMP decomposition at various temperatures.…”

High-Temperature Decomposition of Diisopropyl Methylphosphonate (DIMP) on Alumina: Mechanistic Predictions from Ab Initio Molecular Dynamics

“…The propene end-products predicted by our BOMD simulations corroborates previous experiments on DIMP, which include thermal decomposition studies, 55,56 pyrolysis and combustion in nitrogen/oxygen-rich environments, 57 as well as microwave 28 and laser-induced 30 decomposition under inert environments. Collectively, all of these prior experimental studies detected propene as one of the main by-products of DIMP decomposition, which further supports our BOMD predictions.…”

“…DIMP is the only surrogate with the same isopropyl (-O-C 3 H 7 ) group found in sarin gas (the only structural difference between sarin and DIMP is the substitution of a fluorine for an isopropyl group in the former). Several techniques have also been used to probe DIMP decomposition, including microwave discharge approaches, 28 pyrolysis on porous substrates, 29 laser heating, 30 and thermal decomposition at 700 -800 K. 31 Despite these experimental studies, theoretical analyses of DIMP decomposition on metal oxides are scarce, except for a previous study on mechanism and rates of thermal decomposition of DIMP. 32 In this work, we utilize largescale ab initio molecular dynamics simulations to probe the adsorption dynamics and time scales of DIMP decomposition at various temperatures.…”

The decisive role of pericyclic reactions in the thermal decomposition of organophosphorus compounds

“…Fighting fires in pesticide stockpiles or dimensioning processes for the thermal destruction of nerve agents requires a good knowledge of the reactivity and distribution of products. Despite their high toxicity, few experimental studies have been performed for the destruction of chemical warfare agents [2,3]. Incineration [4,5] belongs to the most widespread methods of destruction envisaged.…”