Thermochemistry of the reactions between CN+ and H2O in the gas phase

The [H-2, C, N, O](+) potential energy surface (PES) has been explored by m eans of high-level ab initio calculations, carried out in the framework of the G2 theory. From this survey we concluded that the predominant products of the CN+ + H2O reaction are the result of the dissociation of HNCOH+ spec ies and to a much lesser extent of the CNHOH+ cation to yield CNH+ +OH. Acc ording to our results HCN+ should not be a product of this reaction because all pathways leading to its formation are unfavourable with regards to oth er competitive processes. Other reactive channels lead to the formation of the H2ONC+ structure which dissociates into CN + H2O+. The loss of NH((3)Si gma) and O(P-3) seems to take place following spin-forbidden reaction paths through an intersystem crossing between the singlet and the triplet PESs. The global minimum of the PES, H2NCO+ is easily accessible and should lead to the loss of carbon monoxide which has not been experimentally observed i n CN+ +H2O reactions. We cannot offer a clear explanation for this disagree ment between theory and experiment.