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.
Xie
Hong-Bin
HB
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
Ding
Yi-Hong
YH
Sun
Chia-Chung
CC
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