STRUCTURE AND REACTIONS OF THE SUCCINIMIDYL RADICAL - A DENSITY-FUNCTIONAL STUDY

Recent density functionals and a variety of basis sets were employed i n the study of three electronic states of the succinimidyl radical in C-2v symmetry: (2)A(1) (sigma(N)), B-2(1) (pi(N)), and B-2(2) (sigma(0 )). The lowest energy sigma(0) state is a genuine (local) minimum, as demonstrated by the harmonic vibrational analysis; the stationary poin ts corresponding to the two remaining states are higher-order saddle p oints on the potential energy surface. Similar results were obtained w ith the Moller-Plesset method, while the complete active space calcula tions predict that the pi(N) state has the lowest total energy. The ri ng-opening reaction from the sigma(0) state is symmetry allowed and wa s calculated with the density functional theory to proceed via a true transition state. The beta-scission process was found to exhibit a lar ge secondary deuterium kinetic isotope effect, with k(H)/k(D) = 1.2. T he infrared spectra of the open forms of the radical that result from beta-scission reaction were calculated and compared to the calculated spectrum of beta-bromopropanoyl isocyanate.