Kinetics of the reactions of silicon compounds. Part 11. Kinetics and mechanism of the gas-phase photochemical reactions between trimethylsilane and 1,1-difluoroethylene

Abstract

The mercury-photosensitised photolysis of gas-phase mixtures of trimethylsilane and 1,1-difluoroethylene has been studied at 30–80 °C, with reactant ratios from 1 : 1 to 12 : 1 and total pressures of 100–600 mmHg, in some cases with added inert gas present. The reaction yields hydrogen (from initiation), the ‘normal’ and ‘reverse’ 1 : 1-adducts (but not in good preparative yield), and the 2 : 1-adduct, but also two vinyltrimethylsilanes in substantial proportions during the early part of the reaction. A free-radical mechanism is presented, steady-state treatment of which is consistent with the observed quantum yields and kinetic behaviour. The effect of inert gas (CF₄) indicates that the deactivation of excited radicals plays a significant role in determining the product distribution.