Radical reaction C3H+NO: a mechanistic study.
Although a number of hydrocarbon radicals including the heavier C(3)-radicals C(3)H(3) and C(3)H(5) have been experimentally shown to deplete NO effectively, no theoretical or experimental attempts have been made on the reactivity of the simplest C(3)-radical towards NO. In this article, we report our detailed mechanistic study on the C(3)H+NO reaction at the Gussian-3//B3LYP/6-31G(d) level by constructing the singlet and triplet electronic state [H,C(3),N,O] potential energy surfaces (PESs). The l-C(3)H+NO reaction is shown to barrierlessly form the entrance isomer HCCCNO followed by the direct O-elimination leading to HCCCN+(3)O on triplet PES, or by successive O-transfer, N-insertion, and CN bond-rupture to generate the product (1)HCCN+CO on singlet PES. The possible singlet-triplet intersystem crossings are also discussed. Thus, the novel reaction l-C(3)H+NO can proceed effectively even at low temperatures and is expected to play an important role in both combustion and interstellar processes. For the c-C(3)H+NO reaction, the initially formed H-cCCC-NO can most favorably isomerize to HCCCNO, and further evolution follows that of the l-C(3)H+NO reaction. Quantitatively, the c-C(3)H+NO reaction can take place barrierlessly on singlet PES, yet it faces a small barrier 2.7 kcal/mol on triplet PES. The results will enrich our understanding of the chemistry of the simplest C(3)-radical in both combustion and interstellar processes, which to date have received little attention despite their importance and available abundant studies on its structural and spectroscopic properties.
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
Hong-Bin
HB
Xie
Yi-Hong
YH
Ding
Chia-Chung
CC
Sun
D003198:Computer Simulation; D005609:Free Radicals / Q000737:chemistry; D006838:Hydrocarbons / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D011789:Quantum Theory
D005609:Free Radicals; D006838:Hydrocarbons; D009569:Nitric Oxide