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Title: One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives

Author
item Uchimiya, Sophie
item GORB, LEONID - Specpro, Inc
item ISAYEV, OLEXANDR - Case Western Reserve University (CWRU)
item QASIM, MOHAMMAD - Us Army Research
item LESZCZYNSKI, JERZY - Us Army Research

Submitted to: Environmental Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2010
Publication Date: 10/1/2010
Citation: Uchimiya,M., Gorb, L., Isayev, O., Qasim, M.M., Leszczynski, J. 2010. One-electron standard reduction potentials of nitroaromatic and cyclic nitramine explosives. Environmental Pollution. 158(10):3048-3053.

Interpretive Summary: One-electron reduction potential is an essential thermodynamic parameter for predicting the contaminant fate in the environment. Although extensive studies have been conducted to understand the degradation pathways of explosives, little information is available on the reduction potentials of different explosives present in shooting ranges. This study utilized experimental and theoretical approaches for determining the one-electron reduction potentials of explosives. The results suggest a thermodynamic trend on the stability of explosives under oxygen-limiting conditions.

Technical Abstract: Extensive studies have been conducted in the past decades to predict the environmental abiotic and biotic redox fate of nitroaromatic and nitramine explosives. However, surprisingly little information is available on one-electron standard reduction potentials (Eo(R-NO2/R-NO2_)). The Eo(R-NO2/R-NO2_) is an essential thermodynamic parameter for predicting the rate and extent of reductive transformation for energetic residues. In this study, experimental (linear free energy relationships) and theoretical (ab initio calculation) approaches were employed to determine Eo(R-NO2/R-NO2_) for nitroaromatic, (caged) cyclic nitramine, and nitroimino explosives that are found in military installations or are emerging contaminants. The results indicate a close agreement between experimental and theoretical Eo(R-NO2/R-NO2_)and suggest a key trend: Eo(R-NO2/R-NO2_) value decreases from di- and tri-nitroaromatic (e.g., 2,4-dinitroanisole) to nitramine (e.g., RDX) to nitroimino compound (e.g., nitroguanidine). The observed trend in Eo(R-NO2/R-NO2_) agrees with reported rate trends for reductive degradation, suggesting a thermodynamic control on the reduction rate under anoxic/suboxic conditions.