Theoretical study on the ion–molecule reaction of NH~+ with CH_2O

摘要

An in-depth theoretical study is carried out at the B3LYP/6-311G(d,p), M062X/aug-cc-pVDZ and CCSD(T)/6-311++G(3df,2dp) (single-point) levels as an attempt to explore the mechanism of the little-understood ion–molecule reaction between NH~+ and CH_2O. Various possible reaction pathways are taken into account. It is shown that six dissociation products, including P_1 (~2N + CH_2OH~+), P_2 (~4N + CH_2OH~+), P_3 (~3NH + CH_2O~+), P_4 (NH_2 + HCO~+), P_5 (NH_3 ~+ CO), and P_9 (H_2 ~+ CONH) are all accessible both kinetically and thermodynamically. Among these products, P_4 is the most competitive product with predominant abundance, and the second most feasible product is P_3, followed by P_2 and P_1. The remaining products, P_5 and P_9, may have negligible yield under room temperature condition. As the intermediates and transition states involved in the NH~+ + CH_2O reaction all stay below the reactant, the title reaction is expected to be rapid, which is consistent with the measured large rate constant in experiment. The present study will enrich our knowledge of the chemistry of NH~+. Furthermore, our calculated result is compared with the previous experimental research, and, meanwhile, it provides a useful guide for understanding analogous reaction, NH~+ with CH_2NH