STRUCTURE AND DISSOCIATION OF THE METHYLDIAZENYL RADICAL - A QUADRATIC CONFIGURATION-INTERACTION COMPUTATIONAL STUDY

The structure and properties of CH3NN, the methyldiazenyl radical, hav e been studied using quadratic configuration interaction (QCI) ab init io calculations. Fully optimized equilibrium and transition state geom etries were located at the QCISD/6-311G* level and the energies at th ese points were evaluated using QCISD(T)6-311G. The intrinsic reactio n coordinate (IRC) for dissociation of the methyldiazenyl radical to f orm N-2 plus CH3 has been traced at the QCISD/6-31G level. These IRC results show that extension of the C-N bond is accompanied by shorteni ng of the N-N bond, contraction of the N-N-C angle, and planarization of the methyl group. Dissociation is found to be exoergic and activate d, with a small activation barrier whose height is estimated to be 630 cm(-1) in a vibrationally adiabatic process. The standard heat of for mation of methyldiazenyl radical is calculated to be 262 kJ/mol. Tunne ling calculations based on the computed IRC profile predict the methyl diazenyl radical to be bound, but short lived, with a maximum lifetime between 10(-11) and 10(-9) s.