KINETICS AND PRODUCT INVESTIGATION OF THE REACTIONS OF VARIOUS ALKYLSILANES WITH OXYGEN-ATOMS [O(P-3)]

The kinetic data of the reactions of allylsilanes with oxygen atoms in the electronic ground state [O(P-3)] were measured in a discharge flo w system in a temperature range between 298 and 770 K. The investigate d alkylsilanes were: monoethylsilane (EtSiH(3)), diethylsilane (Et(2)S iH(2)), triethylsilane (Et(3)SiH) and triisopropylsilane (i-Pr3SiH). T he following Arrhenius expressions for the bimolecular rate constants were obtained: k(monoethylsilane) = (2.4 +/- 0.5) X 10(13) X exp (- 12 20 +/- 120 K/T) cm(3)mol(-1)s(-1) K-diethylsilune = (2.2 +/- 0.4) X 10 (13) X exp (- 1020 +/- 100 K/T) cm(3)mol(-1)s(-1) K-triethylsilane = ( 2.1 +/- 0.4) X 10(13) X exp (- 890 +/- 90 K/T) cm(3)mol(-1)s(-1) K-tri isopropylsilane = (1.9 +/- 0.4) X 10(13) X exp (- 850 +/- 90 K/T) cm(3 )mol(-1)s(-1) The apparent activation energies of these reactions are: E(alpha)(EtSiH(3)) = 10.1 kJ/mol, E(alpha)(Et(2)SiH(2)) = 8.5 kJ/mol, E(alpha)(Et(3)SiH) = 7.4 kJ/mol and E(alpha)(i-Pr3SiH) = 7.1 kJ/mol. The kinetic investigations of the alkylsilanes show, that the number o f the alkyl groups has a significant influence on the rate constant. I n contrast to this, the kind of the alkyl substituents have a minor in fluence on the rate constants. This behaviour is valid for the whole o bserved temperature range. Sensible correlations and product analyses of the reaction of Et(3)SiH with O ((3)p) underline the assumption tha t the first reaction step should be the direct abstraction of a H atom from the silicon.