Infrared multiphoton dissociation of three nitroalkanes

Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision-free thermal chemistry and dynamics of nitromethane, nitroethane, and 2-nitropropane. The isomerization of CH/sub 3/NO/sub 2/ to CH/sub 3/ONO was observed by detecting the CH/sub 3/O and NO products from the dissociation of the internally very hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcal/mol. This method for determining barrier heights shows how a microscopic molecular beam experiment, using infrared multiphoton dissociation where the concept of temperature has no place, can be quantitatively related to pyrolysis experiments which are conducted under collisional, thermal conditions and measure phenomenological quantities such as activation energies.