Density Functional Theory Calculations of the Effect of Fluorine Substitution on the Kinetics of Cyclopropylcarbinyl Radical Ring Openings

DFT calculations (B3LYP/6-311+G(2df,2p)//B3LYP/6-31G(d)) indicate a dramatic impact of fluorine substituents on the structure and reactivity of the cyclopropylcarbinyl radical. Stereoelectronic influences are believed to be largely responsible for the predicted reactivity and regiospecificity of fluorinated radicals such as the 2,2-difluorocyclopropyl carbinyl radical, which has a calculated activation barrier of 1.9 kcal/mol, undergoing regiospecific C 2 −C 3 cleavage to form the 2,2-difluoro homoallylic radical. In contrast, calculations indicate that the 2,2-difluorocyclopropylcarbinyl cation will convert regiospecifically to the 1,1-difluoro homoallylic cation.