Pathways for HCl formation in HO plus ClO reaction

The structure, energetics and the intrinsic reaction coordinate (IRC) pathw ays for the two crucial transition structures, TS3 and DA, leading to HCl f ormation on the singlet CH, Cl, O-2] potential energy surface viz., TS3 DA HOOCl --> (TS3) HCl + O-1(2) and HO2 + Cl --> (DA) HCl + O-1(2) channels ha ve been investigated at different levels of sophistication. Of the two tran sition structures, the latter has been shown to be energetically low-lying compared to the former and the crucial difference between their structures has been identified as the angle of approach of the attacking chlorine atom . The reaction coordinate in both the reactions has been characterized as a complex mode involving a change in all internal coordinates.