"Front Matter". In: Organosilanes in Radical Chemistry - Index of

194 Silyl Radicals in Polymers and Materials
molecular oxygen should be much slower than a diffusion-controlled rate
constant.
EPR investigation on the oxidation of (Me3Si) 2Si(H)Me in benzene at 50 8C
showed some interesting features too [15]. First of all, the measured oxidizability
value kp=(2kt) 1=2 ¼ 1:8 10 2 M 1=2 s 1=2 for this silane is similar to
that of poly(hydrosilane)s when referring to each Si w H moiety. Assuming a
SiMe3 Me3Si O Si O SiMe3 17
O 2
SiMe3 Me3Si O Si
O
O
O SiMe3 18
SiMe3 O
Me3Si O Si
OH
O SiMe3 Scheme 8.5 Reaction sequence for the complete oxidation of (Me3Si) 3SiH
2kt ¼ 1 10 9 M 1 s 1 for radical 14 (R ¼ Me), the rate constants (kp) for the
hydrogen abstraction from (Me3Si) 2Si(H)Me by radical 14 is 6 10 2 M 1 s 1 .
Oxygen consumption of (Me3Si) 2Si(H)Me initiated by photogenerated t-BuO:
radicals in the presence of 14 mM of a-tocopherol, indicated that not all the
silylperoxyl radicals 12 are trapped. Since the rate constant for the reaction of
peroxyl radical with a-tocopherol (under similar experimental conditions) is
4:1 10 6 M 1 s 1 [20], we calculated a rate constant of ca 10 3 s 1 for the
unimolecular reaction of silylperoxyl radical 12, where R ¼ Me.
8.3 FUNCTIONALIZATION OF POLY(HYDROSILANE)S
8.3.1 HALOGENATION
It was reported that the reaction of poly(phenylhydrosilane)
(Mw ¼ 3004, Mw=Mn ¼ 1:79) with CCl4 under room light selectively affords
poly(phenylchlorosilane) along with CHCl3 and CH2Cl2 as by-products (Reaction
8.9) [21]. The replacement of Si w H moieties by Si w Cl is found to be
>84 % or >95 % for reaction periods of 28 h and 5 days, respectively. Vapour
19