EVALUATION OF REACTIVE AND NONREACTIVE PATHS FOR THE INTERACTION BETWEEN O-1(2)((1)DELTA(G)) AND VINYLAMINE USING SEMIEMPIRICAL METHODS

Semiempirical calculations using MINDO/3, MNDO and AMI were conducted on the system vinylamine-singlet molecular oxygen (O-1(2)((1) Delta(g) )) in order to assess, on energetic grounds, the importance of the non reactive path (physical quenching), an approach that has not been cons idered so far. We evaluated the energy differences between the differe nt intermediates already proposed for the photooxidation reaction as w ell as between the located transition states. We have also extended ou r treatment to vinylamine related compounds like ethylene and 1,1 diam inoethylene, so as to decide upon the suitability of the methods on th e basis of the results obtained. The calculations showed for the three methods that, in the absence of solvent, biradical intermediates are more stable than zwitterion or perepoxide, and that the biradical can cyclise to form dioxetane or decompose to yield ground state molecular oxygen. This is in accord with the energetic barriers calculated with MNDO, which seems to be the better method to study the system.