Arrhenius Parameters for the tert-Butoxy Radical Reactions with Trimethylsilane in the Gas Phase

Article abstract of DOI:10.1021/ja00387a049

Arrhenius parameters for the hydrogen abstraction reaction of tert-butoxy radicals with trimethylsilane were measured in the temperature range 43-65 deg C.The absolute rate constants were determined by studying the competitive reactions between tert-butoxy radical decomposition CH3COCH3 + CH3 (4)> and hydrogen abstraction reaction from trimethylsilane t-BuOH + Si(CH3)3 (5)>. Arrhenius parameters for reaction 5 are found to be log A (L/mol*s) = 8.5 and E_a (kcal/mol) = 3.7.For comparison purposes the tert-butoxy radical reaction with the carbon analogue isobutane was also studied.For this reaction log A (L/mol*s) = 8.4 and E_a = 4.3 kcal/mol were obtained.The activation energy and the properties of the activated complex for the trimethylsilane reaction were estimated by using the recently modified BEBO method.The calculated activation energy was in good agreement with the experimental result.The Arrhenius parameters for tert-butoxy radical reactions with various hydrogen donors can be reasonably expressed by the following simple rules: Log A (for reactions with polyatomic hydrogen donors) = 8.4 +/- 0.5 L/mol*s per hydrogen, and E_a (kcal/mol) = 0.42ΔH + 8.7 (+/- 0.7).