- Stationary and Pulsed Photolysis and Pyrolysis of 1,1-Dimethylsilacyclobutane
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A study of the photolysis of 1,1-dimethylsilacyclobutane at 147 - 214 nm shows that of the four primary processes identified the predominant mode of decomposition is to C2H4 and dimethylsilaethene.Evidence from experiments in the presence of SF6 suggests that the dimethylsilaethene is formed initially in a vibrationally excited state: +hν -> Me2SiCH2v + CH2=CH2.Laser pulsed photolysis experiments at 193 nm have been carried out to measure tha absorption spectrum of Me2SiCH2, its absorption cross section, and the rate constant for Me2SCH2 combination: 2Me2SiCH2 -> (Me2SiCH2)2.The values obtained are ? (240 nm, base e) = (1.0 +/- 0.2)E-17 cm2 and k7 = (3.3 +/- 0.8)E-11 cm3 s-1.The kinetics of the pyrolysis of have also been reexamined, yielding the following rate constant expressions: k1/(s-1) = E(15.46 +/- 0.13) exp(-(31043 +/- 218)/T) and k-1/k71/2/(cm3/2s-1/2) = E(-7.0 +/- 0.3) exp(-(7850 +/- 300)/T).From these results, the heat of formation, ?-bond energy, and entropy of Me2SiCH2, have been deduced: ΔHfθ (g, 298 K) = 36 +/- 7 kJ mol-1, B? = 157 +/- 11 kJ mol-1, and Sθ(g, 298 K) = 332 +/- 8 J mol-1 K-1.
- Brix, Th.,Arthur, N. L.,Potzinger, P.
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p. 8193 - 8197
(2007/10/02)
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