Kinetics of the gas-phase reaction between iodine and trimethylsilane and the bond dissociation energy D(Me3Si—H). Part 2

Abstract

The title reaction has been investigated in the temperature range 565–599 K with a view to improving the precision of previous data. The reaction obeyed the rate law –d[I₂]//_dt=k[I₂]_½[Me₃SiH]//_{1 +k′[HI]/[I2]} over a range of iodine and trimethylsilane pressures provided the ratio [Me₃SiH]₀/[I₂]₀ was greater than ≈ 25. At lower values of this ratio, although the data appeared to fit the integrated rate equation, the value of k tended to be high. It is argued that k values at the limiting high reactant ratio represent the true homogeneous reaction. The data are used to obtain log(k₁/dm³ mol^–1 s^–1)=(11.15 ± 0.11)–(87.4 ± 1.2 kJ mol^–1)/RTln 10 for the abstraction reaction I·+ Me₃SiH [graphic omitted] Me₃Si·+ Hi. It is further deduced that the bond dissociation energy, D(Me₃Si—H)= 378 ± 6 kJ mol^–1. This value is in agreement with the previous value (Part 1) although it is more precise.