Reaction of CF3 radicals with group IV tetramethyls

Arrhenius parameters have been measured for the abstraction of hydrogen from the C Si, Ge, and Sn tetramethyls: The rate constants correlate with the proton chemical shift, which is related to a polar effect. In all cases except carbon, a hot-molecule β-fluorine rearrangement-elimination reaction occurs following radical combination: We suggest the occurrence of a radical exchange reaction for the Si, Sn, and Ge systems, with k_exchange (CF₃ + Sn(Me)₄) ～ 10⁷ ml m^?1 s^?1.