Transient species and product formation from electronically excited tetranitromethane

Abstract

Tetranitromethane (TNM) in polar or non-polar solvents was electronically excited with 248 nm, 15 ns pulses from an excimer laser and the transient species formed were detected and characterized with nanosecond time-resolved absorption spectroscopy. The experimental findings indicate that in aerated or deaerated polar solvents the NO₂ radical and the nitroform anion (NO₂)₃C^–, with absorption maximum at 350 nm, are formed. In non-polar solvents, however, electronic excitation of TNM leads to the formation of NO₂ radical and a transient species with absorption maximum at 307 nm, which is attributed to the previously undetected trinitromethyl radical, (NO₂)₃C^˙. Prolonged irradiation of TNM in non-polar solvents results in the formation of nitroform, (NO₂)₃C—H, with an absorption maximum at 290 nm, which is probably generated by (NO₂)₃C^˙via hydrogen abstraction from the solvent. The non-polar solvent radicals generated by the hydrogen-abstraction reaction combine with NO₂ radicals in the solution to form nitroalkane molecules.