REACTIONS OF PHENYLSILANES WITH O(P-3)-ATOMS

The rate constants of the reactions of oxygen atoms with Monophenylsil ane, Diphenylsilane and Triphenylsilane were measured in a flow system . The measurements were carried out in excess of oxygen atoms in a tem perature range 298 K < T < 770 K. For the reactions of the Phenylsilan es with oxygen atoms two main reaction channels are probable. One chan nel is the direct abstraction or an hydrogen atom from the silicon (at tack to the Si - H bond), and the other one is the electrophilic addit ion of the oxygen atom to the aromatic ring. For the reaction of Monop henylsilane and Diphenylsilane with oxygen atoms both reaction channel s have a significant influence on the rate constant. For the reaction of Triphenylsilane the addition of the oxygen atom to the aromatic rin g is the main reaction channel. The measured rate data can be describe d by the following Arrhenius expressions: Monophenylsilane: k(T) = (1. 7 +/- 0.4) . 10(13) . exp(-1380 +/- 140 K/T) cm3 . mol-1 . s-1 Dipheny lsilane: k(T) = (0.7 +/- 0.3) . 10(13) . exp(-1540 +/- 150 K/T) cm3 . mol-1 . s-1 Triphenylsilane: k(T) = (1.3 +/- 0.3) . 10(13) . exp(-1970 +/- 100 K/T) cm3 . mol-1 . s-1. (1) The activation energies of the re actions of the oxygen atoms with Phenylsilanes are 11.5 kJ/mol in the case of Monophenylsilane, 12.8 kJ/mol in the case of Diphenylsilane an d 16.4 kJ/mol in the case of Triphenylsilane.