The Infrared Multiphoton Dissociation of Three Nitrolkanes.
CALIFORNIA UNIV BERKELEY DEPT OF CHEMISTRY
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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 CH3NO2 to CH3ONO was observed by detecting the CH3O and NO products from the dissociation of the very internally hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcalmol. The barrier height determination method was tested and found to give excellent results by applying it to the determintaion of the barrier height to HONO elimination from nitroethane, a value which is well known from activation energy measurements. The method was then applied to the case of HONO elimination from 2-nitropropane and it appears that there is good to believe that the barrier height is 3-5 kcalmol lower in 2-nitropropane than in nitroethane. The success of 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. The concerted HONO elimination reactions from nitroethane and 2-nitropropane were found to channel about 70 and 65 percent of the exist barrier into translation, respectively.
- Physical Chemistry
- Radiation and Nuclear Chemistry