Computational study on the reactions of XO (XÂ =Â F, Cl and Br) with CH3SO and CH3SO2

Potential energy surface (PES) for the reactions of XO (X = F, Cl and Br) with CH3SO and CH3SO2 have been calculated at MP2/6-311++G(d, p)//B3LYP/6-311++G(d, p) level. It is revealed that all the reactions take place on both singlet and triplet surfaces. The reaction mechanisms of XO (X = F, Cl and Br) with CH3SO and CH3SO2 are similar: the hydrogen abstraction channel of singlet-state PES, which has the overall negative activation energy, should be the dominant channel and CH2SO (CH2SO2) + HOX should be the main products. The reactions of CH3SO (CH3SO2) with XO become thermodynamically favored in the sequence of FO, ClO and BrO. The topological analysis of electronic density shows that a four-member-ring structure appears in the dominant reaction pathway, it turns to three-member-ring structure via a T-shaped structure and the ring structure disappears as the reaction proceeds. Furthermore, the scope of the structure transition region, the appeared position of the four-member-ring structure and the position of T-shaped structure correlated well to the atom which linked to the four-member-ring structure.