Thomas N. Bell

Thermal diffusion factors at 300 K for seven binary noble gas systems containing helium or neon

Thermal diffusion factors, αT, have been measured as a function of concentration at 300 K for seven binary noble gas systems containing helium or neon. The results, obtained with a two-bulb cell, are in agreement with those of Saviron et al. who used a thermal diffusion column, and in general greater than those of Taylor et al. who used a 20-tube trennschaukel. The experimental results agree well with values predicted by the Chapmen-Cowling theory and the recent potential functions reported in the literature.

Use of precise binary diffusion coefficients to calibrate two‐bulb cells instead of using the standard end correction for the connecting tube

Precise binary diffusion coefficients, D12, at 300 K have been used to show that the end correction which is normally applied to the connecting tubes of two‐bulb cells is not precise enough when an accuracy of 0.1% in D12 is required. However, two‐bulb cells may be calibrated with the standard diffusion coefficients reported in this paper.

Heats of formation and dissociation of methylsilanes and chlorosilanes and derived radicals

The heats of formation for the complete set of methyl- and chloro-silanes of general formula SiMexClyH4—(x+y), where x= 0–4 and y= 0-(4 –x), have been calculated using the MOBI method. Heats of formation for the radicals and molecules of general formula SiMexClyH3—(x+y), where x= 0–3 and y= 0-(3—x), and SiMexClyH2—(x+y), where x= 0–2 and y= 0-(2—x), have also been computed and a new value for ΔH⊖f(SiMe) is predicted. The heat of dissociation for each Si—H, Si—Cl and Si—C bond in all the above species has been calculated in addition to the heat of dissociation for the Si—Si bond in Si2H6, Si2Me6 and Si2Cl6. Satisfactory agreement with many published experimental data is obtained. The method yields results which are internally consistent, and many quantities, as yet experimentally undetermined, are predicted.

The role of the triplet state in insertion reactions of silylenes

The allowed or forbidden nature of silylene insertion reactions is considered on symmetry grounds together with the consequent energy requirement for such reactions.