Theoretical study on the singlet-state and the triplet-state mechanisms for the reaction CH₃O with NO

Ab initio UHF/6-31G** method have been used to study the reaction mechanism of CH₃O with NO on the singlet and triplet potential energy surfaces. Two parallel reaction channels, leading to products CH₃ONO(a) and HCHO+HNO(b), were separately found on these potential energy surfaces. The Intrinsic Reaction Coordinates (IRC) for the above reactions were traced by using the algorithm of Morokuma. The activation barriers at 6-31G**+ZPE level are 86.86 kJ·mol^-1 and 159.22 kJ·mol^-1 respectively for path(a) and path(b) on the singlet-state surface, and 139.20 kJ·mol^-1 and 196.49 kJ·mol^-1 repectively on the triplet-state surface. The theoretical results show that the reaction occurs more favorably on the singlet-state surface and that CH₃ONO is predominately produced than other products, which is in agreement with the experimental result.