A Theory Study Toward The Reaction Mechanisms Of Typical Explosives With Hydroxyl Radicals

Nitro-aromatic explosives,such as 2,4,6-trinitrotoluene(TNT),2,4-dinitrotoluene(DNT),2,4-dinitrophenyl ether(DNAN),are kinds of energetic compounds used widly in military and civilian.As one of widely used explosives and a class C carcinogen rated by the Environmental Protection Agency(EPA),TNT(2,4,6-trinitrotoluene)is a serious worldwide pollutant that has toxic effect on all living organisms.It can cause toxic liver disease,cataracts,anemia,and oxidative stress poison teratogenic,carcinogenic and other long-term harm.Therefore,explosive degradation treatment is always one of research hotspots.Compared with many degradation techniques,advanced oxidative processes(AOPs)possess simpler process,and higher efficiency in nitroaromatic degradation.The methods employ a variety of highly-active hydroxyl radicals generated chemical methods to attack continuously explosive molecules without selectivity,decompose the molecules into simple small molecules.In recent decades,AOPs have attract much effort on the TNT degradation research.However,the studies mainly focus on the effects of experiment condition and addition on the degradation effect,ignore the detail reaction mechanism.Because of high reaction activity,the detail radical reactions can be hardly observed and determined in experiment.Therefore,it?s necessary to investigate the radical reaction mechanism about the degradation of these explosives using computional chemistry methods.In this work,we used density functional theory method(DFT)with GAUSSIAN 09 program to explore the degradation mechanisms of TNT,DNT and DNAN.At the SMD(Pauling)/M06-2X/6-311+G* level,the properties of intermediates and transition states,including geometries,harmonic vibration frequencies and Gibbs free energies,have been obtained.Combined with existing experimental measures,we reveal the dominant decomposition pathway of TNT is TNT?DNOC(4,6-dinitro-ocresol)? 4,6-dinitro-2-hydroxybenzylalcohol ? 4,6-dinitro-2-hydroxybenzaldehyde.Due to the similar structures,DNT and DNAN have similar decomposition reactions.Dominant decomposition process of DNT is DNT ? 2-nitro-4-hydroxytoluene ? 2-nitro-4-hyroxylbenzylalcohol?2-nitro-4-hydroxybenzaldehyde.Moreover,it? found that hydroxyl radical substitution and hydrogen abstraction are the most important reactions in the decomposition.In the substitution reaction,hydroxyl radical attact to the carbon atom connected with nitro-group,and force the nitro-group to leave the benzene.The processes always have low energy barriers,which refects that the reactions are esay to occur under normal condition.And the reactions are insensitive to the substituent effect on the benzene.Hydroxyl radical abstracts the hydrogen atom on methyl group to initiate the the subsequent oxidation reactions.And methyl group is oxided into aldehyde group.