Hydrogen‐abstraction reactions from organosilicon compounds. The reactions of methyl, trideuteromethyl, trifluoromethyl, and ethyl radicals with tetramethylsilane

The following Arrhenius parameters have been determined for the hydrogen‐abstraction reactions: R + (CH 3 ) 4 Si → RH + (CH 3 ) 3 SiCH 3 R Temp. (°K) E (kcal/mole) Log A (mole −1 cc sec −1 ) Log k (400°K) (mole −1 cc sec −1 ) CF 3 330–433 7.23 ± 0.09 11.90 ± 0.05 7.95 CH 3 396–476 10.23 ± 0.36 11.55 ± 0.18 5.68 CD 3 396–496 10.36 ± 0.12 11.84 ± 0.06 6.20 C 2 H 5 423–522 11.40 ± 0.48 11.88 ± 0.22 5.68 The activation energies are in keeping with the strengths of the bonds formed during the reaction. By comparison with the activation energies for the analogous reactions of neopentane it is estimated that D ((CH 3 ) 3 SiCH 2 H) ≃ 97 kcal/mole. The A factors for the above series of reactions fall within the range predicted by transition‐state theory for this type of process and the validity of previous results of Kerr, Slater, and Young is seriously in doubt.