Theoretical study on the ion–molecule reaction of NH⁺ with CH₂O

Abstract

An in-depth theoretical study is carried out at the B3LYP/6-311G(d,p), M062X/aug-cc-pVDZ and CCSD(T)/6-311þþG(3df,2dp) (single-point) levels as an attempt to explore the mechanism of the little-understood ion-molecule reaction between NH þ and CH 2 O. Various possible reaction pathways are taken into account. It is shown that six dissociation products, including P 1 ( 2 N þ CH 2 OH þ ), P 2 ( 4 N þ CH 2 OH þ ), P 3 ( 3 NH þ CH 2 O þ ), P 4 (NH 2 þ HCO þ ), P 5 (NH þ 3 þ CO), and P 9 (H þ CONH þ 2 ) 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 þ þ CH 2 O 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 þ . Furthermore, our calculated result is compared with the previous experimental research, and, meanwhile, it provides a useful guide for understanding analogous reaction, NH þ with CH 2 NH.