KINETICS AND THERMOCHEMISTRY OF REVERSIBLE ADDUCT FORMATION IN THE REACTION OF CL(P-2J) WITH CS2

Reversible adduct formation in the reaction of Cl(2PJ) with CS2 has been observed over the temperature range 193-258 K by use of time-resolved resonance fluorescence spectroscopy to follow the decay of pulsed-laser-generated Cl(2PJ) into equilibrium with CS2Cl. Rate coefficients for CS2Cl formation and decomposition have been determined as a function of temperature and pressure; hence, the equilibrium constant has been determined as a function of temperature. A second-law analysis of the temperature dependence of KP and heat capacity corrections calculated with use of an assumed CS2Cl structure yields the following thermodynamic parameters for the association reaction: ΔH°298 = -10.5 ± 0.5 kcal mol-1, ΔH°0 = -9.5 ± 0.7 kcal mol-1, ΔS°298 = -26.8 ± 2.4 cal mol-1 deg-1, and ΔHf,298(CS2Cl) = 46.4 ± 0.6 kcal mol-1. The resonance fluorescence detection scheme has been adapted to allow detection of Cl(2PJ) in the presence of large concentrations of O2, thus allowing the CS2Cl + O2 reaction to be investigated. We find that the rate coefficient for CS2Cl + O2 reaction via all channels that do not generate Cl(2PJ) is <2.5 × 10-16 cm3 molecule-1 s-1 at 293 K and 300-Torr total pressure and that the total rate coefficient is <2 × 10-15 cm3 molecule-1 s-1 at 230 K and 30-Torr total pressure. Evidence for reversible adduct formation in the reaction of Cl(2PJ) with COS was sought but not observed, even at temperatures as low as 194 K. © 1990 American Chemical Society.