First Electronic Investigation of the Structure of Alkenes Compatible to Carbon Radicals Bearing a Single Fluorine Atom

Abstract

In order to look into the electronic course of the Michael addition of α-fluorocarbon radical to alkenes, theoretical MO calculations and experiments were attempted. The SOMO values and atomic charges for the α-carbon radical of ethyl β-phenylpropionate (4a) and that of the α-fluoro analog (4b) and HOMO and LUMO values and atomic charges for three representative alkenes, acrylonitrile (6), styrene (7), and propene (8), were calculated using 6-31G and 6-31G* methods. The results are as follows: (i) In the case of simple radicals such as 4a, interaction between the SOMO of radicals and the LUMO of alkenes seems dominant, and therefore, 4a should react with 6 more readily than 7 or 8. (ii) Those radicals having an electron-withdrawing group (EWG) such as fluorine become more electrophilic, considering the energy level differences between the SOMO of radicals and the HOMO and LUMO of alkenes. (iii) The energy level difference between the SOMO of 4b and the HOMO of 7 is smaller than that between the SOMO of 4...