Abstract
The radical‐molecule reaction mechanism of CHCl~2~ and CCl~3~ with NO~2~ have been explored theoretically at the B3LYP/6‐311G(d,p) and MC‐QCISD (single‐point) levels. For the singlet potential energy surface (PES) of CHCl~2~ + NO~2~ reaction, the association of CHCl~2~ with NO~2~ was found to be a barrierless carbon‐to‐nitrogen approach forming an energy‐rich adduct a (HCl~2~CNO~2~) followed by isomerization to b~1~ (trans–cis‐HCl~2~CONO), which can easily interconvert to b~2~, b~3~, and b~4~. Subsequently, the most feasible pathway is the 1,3‐chlorine migration associated with NO1 bond cleavage of b~1~ leading to P~1~ (CHClO + ClNO). The second competitive pathway is the 1,4‐chlorine migration along with NO1 bond rupture of b~4~ giving rise to P~2~ (CHClO + ClON). Moreover, some of P~1~ and P~2~ can further dissociate to give P~6~ (CHClO + Cl + NO). The lesser followed competitive channel is the 1,3‐H‐shift from C to N atom along with NO1 bond rupture of b~1~ to form P~3~ (CCl~2~O + HNO). The concerted 1,4‐H‐shift accompanied by NO1 bond fission of b~3~ to product P~4~ (CCl~2~O + HON) is even much less feasible. For the singlet PES of CCl~3~ + NO~2~ reaction, the only primary product is found to be P~1~ (CCl~2~O + ClNO), which can lead to P~2~ (CCl~2~O + Cl + NO) via dissociation of ClNO. The obtained major products CHClO and CCl~2~O for CHCl~2~ + NO~2~ and CCl~3~ + NO~2~ reactions, respectively, are in good agreement with kinetic detection in experiment. Compared with the singlet pathways, the triplet pathways may have less contributions to both reactions. Because the rate‐determining transition state involved in the feasible pathways lie above the reactants R, the title reactions may be important in high‐temperature processes. The similarities and discrepancies among the CH~n~Cl~3−n~ + NO~2~ (n == 0–2) reactions are discussed in terms of the substitution effect. The present study may be helpful for further experimental investigation of the title reactions. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 661–671, 2006