Ageing mechanisms of nitroethylbenzenes. Issue 2 (3rd April 2019) - Cunningham, Ian D.
ABSTRACT: Simulated ageing of 2, 4-dinitro-1-ethylbenzene (DNEB) in DMSO in the presence of O2 in a closed system at 85–105°C gave benzylic oxidised products 1-(2, 4-dinitrophenyl)ethanol (DNPE) and 2, 4-dinitroacetophenone (DNAP), with the latter as the major product. Evidence for the formation of 3-methyl-6-nitro-2, 1-benzoisoxazole (an 'anthranil'), suggested in the literature as a likely decomposition product, is scant. A mechanism with initial H-abstraction to yield an electron-rich benzylic radical as the rate-limiting step is suggested, supported by a small kinetic isotope effect k H / k D ~2 and a reactivity in the order 2, 4, 6-trinitro-1-ethylbenzene TNEB > DNEB > 4-nitro-1-ethylbenzene (NEB). The activation energy for DNEB oxidation is 40 kJ mol −1, a value that translates to 1% oxidative decomposition of DNEB after ~ 14 d under an O2 atmosphere, or 70 d in air at ambient temperature.