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The static system decomposition kinetics of disilane (Si,H, A SiH, + SiH,, 538-587 K and 10-500 Torr), are reported. Reaction rate constants are weakly pressure dependent. and best fits of the data are realized with RHKM fall-off calculations using IogA,,.

The decomposition kinetics of disilane with added butadiene, trisilane both neat and with added butadiene, trimethylsilane or H,, and normal and iso-tetrasilane both neat and in the presence of added butadiene are reported. Arrhenius parameters of the primary dissociation reactions are determined: A-factors suggest that polysilane decompositions (1) have similar intrinsic activation entropies (AS* = 6.2 ? 5 e.u.1 and (2) have activation energies which increase with increasing reaction endothermicities. Relative trapping efficiencies of SiH,, Si,H6, SiBH8, C4Hs, Me,SiH, and Hz toward SiHz and SiH,SiH are also determined. Other results include the heat of formation of silylsilylene, AH; (SiH,SiH) = 75.3 Kcal/mol, and the activation energy for 1,l-H, elimination from disilane (EH2 = 57.8 kcal/mol).

PARASKEVOPOULOS. Can. J. Chem. 61, 861 (1983). A kinetic study of the reactions of OH radicals with a series of fluoroethanes in the gas phase is prcsented. OH radicals were generated by flash photolysis of H 2 0 vapor in the vacuum uv (A > 165 nm) and were monitored in absorption by timc-rcsolved attenuation of resonance radiation at 308.15 nm [OH(A'C' + X'n)]. The following absolute rate constants (in units of 10%m3 mol-' s-I at the 95% confidence limit) were determined at 298 K: kcli2rcli,r = 67.7 + 7.2, kC~2FClIF2 = 11.0 + 1.1, ~C H~C F~ = 1.03 20.26, kCHZFCFl = 3.10 2 0.35. kCHF2CF3 = 1.50 I+--0.17. From a linear correlation of the present and previously published rate constants with bond dissociation energies, the following quantities (in kcal mol-' at 298 K) were estimated to be: D(CH,CHF-H) = 96.3 5 .1.5, D(CH,FCHF-H = 98.8 5 .