The reaction Si(CH3)3 + HBr → Si(CH3)3H + Br (1) has been investigated using flash photolysis/ photoionization mass spectrometry detection of Si(CH3)3 and flash photolysis/resonance fluorescence spectroscopy detection of Br. The measured rate constants are k1 = (1.06 ± 0.13) × 10-11 exp((6.14 ± 0.31) kJ mol-1/RT) cm3 molecule-1 s-1 for T = 296-702 K and k1 = (8.1 ± 2.0) × 10-12 exp((5.12 ± 0.72) kJ mol-1/RT) cm3 molecule-1 s-1 for T = 289-515 K, respectively. The 1σ uncertainties represent precision only. Combination with k-1 data and analysis by second and third law methods yields ΔH°298 = -31.1 kJ mol-1 for (1), with accuracy limits of about ±2.0 kJ mol-1. The results imply an Si-H bond dissociation enthalpy of 397.4 ±2 kJ mol-1 and an enthalpy of formation for trimethylsilyl of 16.4 ± 6.0 kJ mol-1.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry