Kinetics and thermochemistry of ClCO formation from the Cl+CO association reaction

Abstract

Laser flash photolysis of Cl2/CO/M mixtures (M=N2, CO, Ar, CO2) has been employed in conjunction with Cl(2PJ) detection by time-resolved resonance fluorescence spectroscopy to investigate equilibration kinetics in the reactions Cl(2PJ) +CO↔ClCO as a function of temperature (185–260 K) and pressure (14–200 Torr). The association and dissociation reactions are found to be in the low-pressure limit over the range of experimental conditions investigated. In N2 and/or CO buffer gases, the temperature dependences of the ClCO formation and dissociation reaction rate constants are described by the Arrhenius expressions k1=(1.05±0.36)×10−34 exp[(810±70)/T] cm6 molecule−2 s−1 and k−1=(4.1±3.1)×10−10 exp[(−2960±160)/T] cm3 molecule−1 s−1 (errors are 2σ). Second- and third-law analyses of the temperature dependence of the equilibrium constant (k1/k−1) lead to the following thermodynamic parameters for the association reaction: ΔH0298 =−7.7±0.6 kcal mol−1, ΔH00 =−6.9±0.7 kcal mol−1, ΔS0298 =−23.8±2.0 cal mole−1 K−1, ΔH0f,298 (ClCO)=5.2±0.6 kcal mol−1 (errors are 2σ). The results reported in this study significantly reduce the uncertainties in all reported kinetic and thermodynamic parameters.