(652c) Analysis of Di- and Tri- Nitroaromatic Analogues of TNT: Rates and Reactivities of Transformation Pathways

This research compared 2,4,6-trinitrotoluene (TNT) to 1,3,5-trinitrobenzene (TNB); 2,4,6-trinitrophenol (picric acid or TNP); 1,3-dinitrobenzene (DNB); 2,4- and 2,6 dinitrotoluene (DNT) and 2,4-dinitroanisole (DNAN). The hypothesis, molecular structure determines preferred transformation pathways that can be theoretically predicted and spectroscopically verified, was utilized to evaluate rates and mechanisms of these aromatic compounds and their intermediates as relating to their structures and possible environmental impacts.

Quantum and classical mechanical computational (MOPAC and DFT) methods were used to characterize selected properties: heat of formation; HOMO and LUMO energies; charge density of the g system; and dipole moment prior to our experimental approach, in which two experimental transformation methods compared the effectiveness of alkaline hydrolysis (using sodium hydroxide [NaOH]) with photolysis (using monochromatic irradiation at respective absorption maxima).

UV/Vis spectra were taken and major peaks of parent compounds identified prior to addition of NaOH. Upon addition of varied concentrations of NaOH, both transformation of parent compound peaks and formation of new transition product peaks were observed. These peaks were further evaluated via Stopped Flow (SF) spectroscopy to obtain reaction kinetics. UV/Vis data were supported by corresponding results with SF spectra. UV/Vis and SF data were then compared to the CC data for all possible transition states, intermediates, and final products to discern which compounds comprise chemically and energetically feasible transformation products. Comparisons of the following groups were based on molecular structure and number/position of substituents: i) TNT and TNB; ii) DNAN, DNB, DNT and DNP; iii) TNT and DNT; iv) DNB and TNB.

Significant trends were revealed among these groups. Our CC and experimental data revealed that type, number and position of substituents determine reaction rates and reactivities and, therefore, potential environmental impacts.