THEORETICAL-STUDY ON THE MECHANISM AND REACTIVITY OF FLUOROCUMULENES IN [4-CYCLOADDITIONS(2])

Semi-empirical molecular orbital calculations have been used to invest igate the transition structures and energetics of the [4+2] cyclo-addi tion reactions of butadiene with allene, monofluoroallene, I,1-difluor oallene and trifluoroallene. Geometry optimizations have been performe d with both AM1 and PM3 Hamiltonians and on the basis of the computed transition state geometries and activation energies, the favoured ster eochemical preferences of the reactions and the reactivity of fluorall enes have been predicted. The reactivity order found agrees well with ab initio predictions based on LUMO energies and experimental observat ions.