The hydrogen abstraction reactions of tert-butoxyl radicals with germane, phosphine, and trimethylsilane were studied by pyrolyzing di-t-butyl peroxide in the temperature range of 403 to 458 K. From the reported rate constant for the tert-butoxy radical decomposition in the literature, the absolute rate constants were determined from the study of competitive reaction between t-butoxy radical decomposition (t-BuO decompose+ CH3COCH3 + CH,) and hydrogen abstraction reaction. (t-BuO RH -+ t-BuOH + R, where RH = GeH,, PH,, and HSiMe,)The Arrhenius parameters are found to be as follows:E,(kcal mol-') Log A t-BuO + SiHMe, 2.1 t-BuO + GeH,
1.9t-BuO + PH3