AB-INITIO THEORETICAL-STUDIES ON THE RING-OPENING MODES OF THE OXIRANYLMETHYL, AZIRIDINYLMETHYL, OXAZIRIDINYLMETHYL, AND THIARANYLMETHYL RADICAL SYSTEMS

Ab initio theoretical studies have been carried out on the oxiranyl-, aziridinyl-, oxaziridinyl-, and thiaranylmethyl radical systems and on the various possible conformations of the ring-opened heteroallyllic radical systems derived by ring opening of the First three systems. Pr evious theoretical studies on the ring opening of the oxiranylmethyl r adical indicated that there is an overwhelming thermodynamic preferenc e for the formation of the allyloxy radical over the formation of the (vinyloxy)methyl radical. The results of the present theoretical studi es on the potential energy surfaces for ring opening also indicate a s trong kinetic preference for allyloxy radical formation over the forma tion of the (vinyloxy)methyl radical. The results of the present calcu lations on the aziridinylmethyl radical indicates that it kinetically prefers to ring open by cleavage of the C-N bond, but thermodynamicall y by cleavage of the C-C bond. The results of the calculations on the C2H4NO radical system indicate that ring opening of the oxaziridinylme thyl radical by C-O bond cleavage is both thermodynamically and kineti cally favored over C-N bond cleavage. Calculations on the thiaranylmet hyl radical suggest that it does not represent a minimum-energy struct ure on the C3H5S potential energy surface.