Chemically Activated Tetramethylsilane from the Reaction of Singlet Methylene Radicals with Trimethylsilane

An experimental study of the photolysis of trimethylsilane–diazomethane–oxygen mixtures and tetramethylsilane–trimethylsilane–diazomethane–oxygen mixtures at 4358 and 3660 Å is reported. Experimental rate constants for the decomposition of chemically activated ethyltrimethylsilane, ethyldimethylsilane, and tetramethylsilane are determined. These specific rates range from 3 × 104 sec−1 to 6.5 × 105 sec−1. A comparison of the 4358- and 3660-Å rate constants for tetramethylsilane decomposition with RRKM theory calculations suggest that a thermal A factor of 1015.0±0.5 sec−1 is correct for primary decomposition by Si–C bond rupture. The uncertainty in this A factor reflects the uncertainties in the E* and E0 values for chemically activated tetramethylsilane. A discussion of this A factor relative to that found previously for neopentane decomposition is given.