Ab initio molecular orbital study of the mechanism of photodissociation offormamide

In the present Letter, the reaction pathways for H2NCHO decomposition in th e ground and excited states are traced with the use of the MP2 and CASSCF e nergy gradient techniques. The intersection point of the S-1 and T-1 surfac es are determined by means of the state-average CASSCF optimization. The n --> pi* excitation leads to the first excited singlet state, where a radica l pair of NH2 and CHO is formed. Then a hydrogen atom transfers from the CH O radical to the NH2 radical, producing CO and NH3 in the ground state. Thi s is in good agreement with recent experimental findings. The calculated re sults also show that H-2 and HNCO can be formed along a two-step T-1 pathwa y. A recent experimental study on the photochemistry of the H2NCHO suggeste d that H-2 elimination from H2NCHO takes place on the T-1 surface. (C) 2000 Elsevier Science B.V. All rights reserved.