Thermal Decomposition of Sulfur Mustard: Pyrolysis Experiments in the Presence of Radical Scavengers, Single Pulse Shock Tube Experiments, and Kinetic Modeling

The thermal decomposition kinetics and mechanism of Sulfur Mustard, a typical chemical warfare agent, were studied through Py-GC/MS experiments, Single Pulse Shock Tube experiments, and theoretical calculations. The cleavage of the C-S bond was demonstrated to be the initial reaction pathway in the pyrolysis of Sulfur Mustard, as evidenced by the introduction of a radical scavenger in the Py-GC/MS experiment, which terminated the reaction at its nascent stage. Based on the effective carbon number method, the experimentally observed overall rate constant for thermal decomposition of Sulfur Mustard was found to be k = 10(21.97 ± 1.29)exp(-(17434.74 ± 1193.39)/T) s-1 between 782 and 1058 K. A kinetic model for the thermal decomposition of Sulfur Mustard was developed, based on quantum chemical calculations and transition state theory, in combination with experimental data. This model provided a satisfactory elucidation for the decomposition rate and major products of Sulfur Mustard. The thermal decomposition of Sulfur Mustard primarily proceeds through channels such as chlorine atom abstraction of hydrogen from the secondary carbon, intramolecular elimination of hydrogen chloride, and C-S bond cleavage.