An ab initio MO study of perfluoro-effect in thermal cyclization of buta-1,3-diene to cyclobutene

Abstract

Ab initio theoretical studies at SCF and MP2 levels with various basis sets on thermal cyclization of perfluorobuta-1,3-diene to perfluorocyclobutene confirm the experimentally observed reversal of relative stabilities on perfluorination of buta-1,3-diene (1) and cyclobutene . The transition structures follow Hammond's postulate. The effect of fluorine substitution on sp² and sp³ hybridized carbon centres are analysed using the relative energies of mono-, di-, tri- and tetra- fluoroderivatives of butadiene and cyclobutene at HF/6-31G* level. The reversal of relative stabilities of perfluorination is attributed to the increasing destabilization on polyfluorination at sp²-C.