Fluoroolefin condensation catalyzed by aluminum chlorofluoride

Article abstract of DOI:10.1016/0022-1139(96)03388-X

High-fluorine-content aluminum chlorofluoride, as prepared by Cl/F exchange of aluminum chloride with one of a number of organofluorine compounds, is a very active Lewis acid capable of condensing an allylic fluoride with another fluoroolefin at low temperature. In addition to a description of broader scope, details of the selective reaction of hexafluoropropene with tetrafluoroethylene to form F-pentene-2 are presented along with evidence supporting polyfluoroallyl cationic species as intermediates. Ab initio calculations confirm the feasibility of the proposed mechanism and further suggest that 1,3-fluorine shifts in fluorocarbocations are energetically accessible at modest temperatures. Revised heats of formation for C₃F₈ (ΔH⁰_f = - 1750 ± 12.4 kJ mol^-1) and HFP (ΔH⁰_f = - 1128 ± 5 kJ mol^-1) have been calculated. Fluoride affinities of some simple metallohalogens are reported.