Issue 15, 2001

Pressure and temperature dependence of the gas-phase reaction of silylene with dimethyl ether

Abstract

Gas-phase reaction rate constants for the reaction of silylene, SiH2, with dimethyl ether, CH3OCH3 have been determined over the temperature range 294–441 K and at total pressures of inert bath gas (Ar or SF6) over the range 30–850 Torr. The second-order rate constants are pressure dependent, even up to the maximum pressure investigated of 850 Torr, and the rate constants decrease with increasing temperature, indicating that the reaction proceeds [italic v (to differentiate from Times ital nu)]ia the formation of a complex. At the highest temperature studied (441 K), the experimental decay curves do not return to the baseline. This is attributed to the system reaching equilibrium, with SiH2 being produced by dissociation of the complex, and provides direct experimental evidence for the formation of the complex. Analysis of the decay curves provided an experimental determination of the equilibrium constant, Keq, at 441 K. The high-pressure rate constants, obtained by extrapolation of the experimental data using RRKM/master equation modelling, yield the Arrhenius parameters log (A/cm3 molecule−1 s−1) = − 7.6 ± 0.4 and Ea = 9.3 ± 2.8 kJ mol−1. The RRKM/master equation modelling gives a well depth for the SiH2–CH3OCH3 complex of 87 kJ mol−1. This compares with a value of 88.4 ± 1.7 kJ mol−1 determined from Keq at 441 K. Ab initio calculations, performed at the MP2/6-311 + G** level of theory, give a well-depth for the complex of 82.9 kJ mol−1, in excellent agreement with this value.

Article information

Article type
Paper
Submitted
02 Jan 2001
Accepted
25 May 2001
First published
29 Jun 2001

Phys. Chem. Chem. Phys., 2001,3, 3085-3094

Pressure and temperature dependence of the gas-phase reaction of silylene with dimethyl ether

U. N. Alexander, K. D. King and W. D. Lawrance, Phys. Chem. Chem. Phys., 2001, 3, 3085 DOI: 10.1039/B100068N

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