Double methyl substitution in simple alkenes leads to low-barrier reactions towards molecular fluorine

The reactions of F2 with isomers of butene were investigated with crossed-beam reactive scattering and ab initio computations. Only one product channel F + C4H8F was observed in the experiments; the HF + C4H7F channel was searched but not found. The reaction path of F2 + C4H8 → F + C4H8F was studied theoretically. Very low barriers of less than 1 kcal/mol were found for the F2 reactions with cis-2-butene, trans-2-butene, and isobutene, which all contain two methyl substitution groups. This theoretical prediction, yet to be confirmed experimentally, suggests that double methyl substituted CC double bonds can react with F2 almost without a barrier.