Theoretical study on the gas phase reaction of CHO + NH: the formation of CHONH, NHCHOH, or CHNH + HO.

The gas phase reaction between CHO and NH is an important reaction in cold interstellar clouds, combustion chemistry and organic chemistry. In this study, the stationary point on the potential energy surfaces (PESs) for the CHO + NH reaction was computed at the CCSD(T)/6-311++G(3df,3pd)//M06-2X/6-311++G(3df,3pd) level. The temperature- and pressure-dependent rate constants were computed using advanced kinetic models, including microcanonical variational transition state theory and Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation (ME) techniques. Our result predicts that the CHO + NH reaction forms a collisionally thermalized CHONH complex with respect to thermal unimolecular dissociation and the other products, i.e., NHCHOH and CHNH + HO, are negligible under atmospheric conditions. The calculated atmospheric lifetime of the CHONH complex is ∼17 min, which suggests that the CHONH complex can react with other atmospheric species. The results also suggest that the formation of CHNH and HO from the Strecker's process is negligibly small under all the conditions studied here. The decay rate of CHO + NH (5.1 × 10 s at 1500 K) suggests that aminomethanol (NHCHOH) is likely to occur in the high-temperature combustion of biomass burning, but the rate of formation of NHCHOH is negligible under atmospheric conditions. The predicted atmospheric lifetime (∼4 days) of NHCHOH in the presence of the OH radical suggests that further reactions with other atmospheric species are possible. The formation of the NHCHOH radical from the reaction OH + NHCHOH can lead to carcinogenic products, such as nitrosamines, acetamide, hydrocycnic acid, NH and CO.