Equilibrium Constants of the Reaction of Cl with O2 in the Formation of ClOO

The equilibrium constants for the formation of ClOO from Cl and O 2 are experimentally measured at 212−245 K using cavity ring-down spectroscopy. A van't Hoff plot analysis yields Δ H r = 4.8 ± 1.5 kcal mol -1 . The Cl−OO bond dissociation energy is determined to be 4.69 ± 0.10 kcal mol -1 from the present and previously reported temperature dependences of the equilibrium constant by the third-law analysis utilizing our recent accurate rotational spectroscopic data. High level ab initio calculations using MRSDCI+Q with the complete basis set extrapolation are also performed. The present ab initio calculations yield the Cl−OO bond dissociation energy to be 4.56 kcal mol -1 .