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Topological analysis of the electron localization function applied to the study of the [1,3] sigmatropic shift of fluorine in 3-fluorpropene

The [1,3] sigmatropic shift of the fluorine atom in the 3-fluorpropene system has been studied from the topological analysis of the electron localization function (ELF). All calculations have been carried out at the B3PW91/6-311g** level of theory. The allowed suprafacial pathway through a concerted four-membered Cs transition state (TS) has been characterized in terms of an ion pair structure which shows the halogen atom bearing −0.6e. The ionic nature of the TS is supported by the absence of any polisynaptic basin connecting the fluorine and the allyl fragments in this stationary point. Finally, the evolution of the bonding characteristics along the intrinsic reaction coordinate reaction path has been analyzed in detail in terms of the basin properties of the ELF function.