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

Carbon-Centred Radicals 35
R R
Si
X
Y
H
8 R = t-Bu, X = O, Y = H
9 R = t-Bu, X = O, Y = Ph
10 R = t-Bu, X =CH 2, Y = H
11 R = Ph, X = CH 2, Y = H
R
Si
R
Reactions (3.5)–(3.7), where u ¼ 2:3RT kJ/mol, combined with the Arrhenius
parameters for the reaction of primary alkyl radicals with (Me3Si) 3SiH
afford the temperature-dependent function for the unimolecular reactions.
It is worth mentioning that the calibration of these radical clocks is based
on the assumption that the radicals 12, 13 and 14 will react with (Me3Si) 3SiH
with a rate constants equal to that of a simple model of primary alkyl radical
3. This is reasonable for the radical 12 and 13, whereas the influence of a-amide
group in radical 14 is unknown, although it is expected to be similar based on
the knowledge of the reactivity of Group 14 hydrides [1].
O
RSCH 2 CH 2
k f
Y
X
RS + H 2 C = CH 2
log k H /k f (M −1) = − 5.4 + 25.9/θ
log k f/s −1 = 14.2 − 44.4/θ
CO 2 Me
k re
13 log k H /k re (M −1 ) = − 1.7 + 14.6/θ
log k re /s −1 = 10.6 − 33.5/θ
N
CH3 O
CO 2 Me
kc O N
CH3 O
14 log k H/k c(M −1 ) = −1.9 + 18.4/θ
log k c/s −1 = 10.8 − 37.2/θ
(3.4)
(3.5)
(3.6)
(3.7)