Ab initio studies of ClOx reactions. VII. Isomers of Cl2O3 and their roles in the ClO+OClO reaction

Abstract

The mechanism for the reaction ClO+OClO has been investigated by ab initio molecular orbital and transition state theory calculations. Nine stable isomers of Cl2O3 (including optical isomers) are located at the B3LYP/6-311+G(3df ) level. The transition states between pairs of isomers are explored and the stability of the isomers and their dissociation mechanisms are discussed. The relative stability predicted by the modified Gaussian-2 (G2M) method at the G2M//B3LYP/6-311+G(3df ) level is ClOCl(O)O>ClOOOCl(C2)>ClOOOCl(Cs)>ClClO3(C3v)>cyc-ClOOCl(O)>ClOOClO. The formation of ClOCl(O)O is dominant at low temperatures, taking place barrierlessly with the second and third order rate constant, k1∞=3.0×10−10 cm3 molecule−1 s−1 and k10=1.1×10−17 T−5.5 exp(−398/T) cm6 molecule−2 s−1 in the temperature range of 200–400 K for N2 as the third-body. Over 500 K, formation of ClOO+ClO becomes dominant and ClOCl+1O2 is also competitive. Their overall rate constants can be given by kClOO=1.0×10−22 T2.8 exp(−78/T) and kClOCl=9.6×10−22 T2.4 exp(−1670/T)cm3 molecule−1 s−1, respectively, in the temperature range of 500–2500 K.