Date of Award
Doctor of Philosophy (PhD)
Chemistry and Biochemistry
Craig A. Bayse
The underlying mechanisms of chemical warfare agents (CWAs) and high energy density materials (HEDMs) are poorly understood, yet important to the development of chemical applications in military science and technology. The reactivity of arsenite and arsenic-based CWA lewisite with biological thiols plays an important role in toxicity of these elements. Toxic effects of arsenite are eliminated when arsenite and selenite are co-administered, due to their antagonistic relationship. The arsenic-based CWA lewisite is detoxified by the dithiol-containing British anti-lewisite (BAL). The reduction of arsenous acid by thiol, the formation of an As-Se species, and the detoxification of lewisite with BAL have been modeled using density functional theory (DFT) and solvent-assisted proton exchange (SAPE), a microsolvation technique that uses a network of water molecules to mimic the participation of bulk solvent in proton transfer processes. Several pathways were explored for the formation of an As-Se bond with the nucleophilic attack of selenide on (RS)2AsOH to form (RS)2AsSeH as the most likely, consistent with previous experimental studies. DFT-SAPE activation barriers for the two-step detoxification of lewisite with BAL predict rapid formation of a ring product, also observed experimentally.
The initial step in the decomposition of HEDMs is not yet understood due to the rapid rate at which the reaction takes place. Trigger bonds, or bonds that break to initiate explosive decomposition, were characterized using Wiberg bond indices (WBIs) for known HEDMs RDX, HMX, TNT, PETN, for comparison to recently-synthesized tetrazole-based explosives. WBIs were compared to reference compounds to determine the degree of weakening in bond strength (ΔWBI) to show that N-NO2, C-NO2, and O-NO2 bonds are likely to cleave initially, consistent with previous experimental and theoretical results. Tetrazole-based molecules with small side chains and one –NO2 group are predicted to have an N-NO2 trigger bond. Larger side chains with one –NO2 group are predicted to break in the C-N side chain backbone. Molecules with more than one –NO2 will cleave at the C-N bond from tetrazole.
Harper, Lenora K..
"Computational Investigation of Pernicious Compounds: Arsenic and High Energy Density Materials and Their relevant Mechanisms"
(2015). Doctor of Philosophy (PhD), Dissertation, Chemistry and Biochemistry, Old Dominion University, DOI: 10.25777/0xs9-pc36