Structural Characteristics and Reactivity Relationships of Nitroaromatic and Nitramine Explosives – A Review of Our Computational Chemistry and Spectroscopic Research

Abstract

Although much has been discovered, discussed and written as to problems of contamination by various military unique compounds, particularly by the nitrogen based energetics (NOCs), remaining problems dictate further evaluation of actual and potential risk to the environment by these energetics and their derivatives and metabolites through determination of their environmental impact-transport, fate and toxicity. This work comprises an effort to understand structural relationships and degradation mechanisms of current and emerging explosives, including nitroaromatic; cyclic and cage cyclic nitramine; and a nitrocubane. This review of our computational chemistry and spectroscopic research describes and compares competitive degradation mechanisms by free radical oxidative, reductive and alkali hydrolysis, relating them, when possible, to environmental risk.

Arabidopsis Glutathione Transferases U24 and U25 Exhibit a Range of Detoxification Activities with the Environmental Pollutant and Explosive, 2,4,6-Trinitrotoluene

“…GST-U25 can directly conjugate glutathione to TNT, via the removal of a nitro group, producing 2-glutathionyl-4,6-dinitrotoluene. The removal of a nitro group from TNT is highly desirable; it is the presence of the electron-withdrawing nitro groups on the TNT molecule that provides stability to the aromatic ring through resonance (Qasim et al, 2007). The denitration activity of GST-U25 presents the opportunity for subsequent degradation and mineralization of TNT, rather than the indefinite storage of TNT-transformation products in the environment.…”

“…The most commonly used explosives in military weapons are 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and their continual use, along with production and decommissioning, are progressively contaminating millions of hectares of military land . Bioremediation of TNT is particularly challenging, as the electron-withdrawing properties of the three nitro groups render the aromatic ring particularly resistant to oxidative attack and ring cleavage by microbial oxygenases, which in the environment are normally central to the biodegradation of aromatic compounds (Qasim et al, 2007). In the United States, the Environmental Protection Agency and the military are addressing methods by which toxic TNT and RDX can be contained and detoxified on active military training ranges.…”

Soil Contamination in Areas Impacted by Military Activities: A Critical Review

“…Some explosives such as nitroglycerin (NG) and pentaerythritol tetranitrate (PETN) are seldom found in soils; therefore, the studies addressing them in the soil are scarce [86,87]. Table 4 shows the physio-chemical characteristics of selected explosive compounds, each of which have the potential to pose specific environmental risks as discussed later [4,11,[88][89][90]. Table 5 presents a summary of the sampling studies of explosive compounds for surface and subsurface soil at different military ranges [6,8,79,.…”

The Sycamore Maple Bacterial Culture Collection From a TNT Polluted Site Shows Novel Plant-Growth Promoting and Explosives Degrading Bacteria

“…In general, TNT-transformation in aerobic soils is mediated by bacterial nitroreductases found amongst the genera Achromobacter , Enterobacter , Klebsiella , Pseudomonas , and others leading to the formation of amino-metabolites which are less bioavailable and less toxic than the parent compound ( Boopathy et al, 1994 ; French et al, 1998 ; Labidi et al, 2001 ; Kim et al, 2002 ; Caballero et al, 2005 ; Gonzalez-Perez et al, 2007 ; Neuwoehner et al, 2007 ; van Dillewijn et al, 2008b ; Rahal and Moussa, 2011 ; Thijs et al, 2014a ; Iman et al, 2017 ). However, natural TNT degradation is extremely slow due to the chemical structure of TNT which renders it particularly resistant to oxidative attack, ring cleavage and thus mineralization ( Qasim et al, 2007 ). In addition, TNT can have a low bio-availability as a consequence of irreversible binding with humic acids, clay and organic matter, and also harsh environmental conditions, e.g., nutrient limitations, co-pollutants and high toxicity, are not promotive of TNT degradation.…”