Speciation of the products of and establishing the role of water in the reaction of TNT with hydroxide and amines: structure, kinetics, and computational results.

The reaction of trinitrotoluene (TNT) with bases has been investigated by NMR and visible spectroscopy methods. Hydroxide ion was found to react in one of two ways, either by deprotonation of the methyl group or by nucleophilic attack on the aromatic ring to form a σ adduct. The rate of each mode of reaction depends upon the polarity of the solvent. In tetrahydrofuran (THF), σ adduct formation is rapid and the long-term equilibrium product is deprotonation of the methyl group. When the solvent is methanol (MeOH), the two reactions have similar rates and the σ adduct becomes the majority product. Amines were found to be ineffective in directly deprotonating TNT or in forming σ adducts. Rather, the amines react with ambient water to generate hydroxide ion, which then reacts with TNT. The solvent choice and water content are crucial to understanding the reactivity of bases with TNT. To assist in the interpretation of the experimental results, computational analysis was performed at the B3LYP/6-311+G**//HF/6-311+G** level to determine the thermodynamics of the reactions of TNT. The SM8 implicit solvation model was applied to converged geometries and suggested a strong solvation effect upon product formation. Thermodynamic analysis suggested a significant preference of alkoxide or hydroxide attack versus amine attack in any modeled dielectric, consistent with the experimental observations.

Fluorescent species formed by reaction of trinitroaromatics with N,N-dimethylformamide and hydroxide.

Trinitrobenzene (TNB) and trinitrotoluene (TNT) react in N,N-dimethylformamide (DMF) to form multiple species in solution. Despite structural similarities, electronic spectra show that the reactivity is different for TNB and TNT. In addition to reaction with the DMF solvent, residual water in nominally dry DMF generates sufficient hydroxide for reaction with TNB and TNT. Multiple sigma adducts are formed and observed to be fluorescent, which has not been previously reported. Both TNB and TNT show the capacity to form sigma adducts with hydroxide and DMF, while methyl hydrogens of TNT can be deprotonated by hydroxide.