Jin Lin, Ding Yi-Hong, Wang Jian, Sun Chia-Chung
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China.
J Comput Chem. 2006 May;27(7):883-93. doi: 10.1002/jcc.20396.
To investigate the possibility of the carbyne radical CCN in removal of nitric oxide, a detailed computational study is performed at the Gaussian-3//B3LYP/6-31G(d) level on the CCN + NO reaction by constructing the singlet and triplet electronic state [C(2)N(2)O] potential energy surfaces (PESs). The barrierless formation of the chain-like isomers NCCNO (singlet at -106.5, triplet cis at -48.2 and triplet trans at -47.6 kcal/mol) is the most favorable entrance attack on both singlet and triplet PESs. Subsequently, the singlet NCCNO takes an O-transfer to form the branched intermediate singlet NCC(O)N (-85.6), which can lead to the fragments CN + NCO (-51.2) via the intermediate singlet NCOCN (-120.3). The simpler evolution of the triplet NCCNO is the direct N-O rupture to form the weakly bound complex triplet NCCN...O (-56.2) before the final fragmentation to NCCN + (3)O (-53.5). However, the lower lying products (3)NCN + CO (-105.6) and (3)CNN + CO (-74.6) are kinetically much less competitive. All the involved transition states for generation of CN + NCO and NCCN + (3)O lie much lower than the reactants. Thus, the novel reaction CCN + NO can proceed effectively even at low temperatures and is expected to play a role in both combustion and interstellar processes. Significant differences are found on the singlet PES between the CCN + NO and CH + NO reaction mechanisms.
为了研究卡宾自由基CCN去除一氧化氮的可能性，通过构建单重态和三重态电子态[C(2)N(2)O]势能面（PESs），在Gaussian-3//B3LYP/6-31G(d)水平上对CCN + NO反应进行了详细的计算研究。链状异构体NCCNO（单重态为-106.5 kcal/mol，三重态顺式为-48.2 kcal/mol，三重态反式为-47.6 kcal/mol）的无势垒形成是单重态和三重态PESs上最有利的初始进攻方式。随后，单重态NCCNO发生氧转移形成支链中间体单重态NCC(O)N（-85.6 kcal/mol），其可通过中间体单重态NCOCN（-120.3 kcal/mol）生成碎片CN + NCO（-51.2 kcal/mol）。三重态NCCNO更简单的演化过程是直接发生N-O断裂，在最终裂解为NCCN + (3)O（-53.5 kcal/mol）之前形成弱结合复合物三重态NCCN...O（-56.2 kcal/mol）。然而，能量较低的产物(3)NCN + CO（-105.6 kcal/mol）和(3)CNN + CO（-74.6 kcal/mol）在动力学上竞争力要小得多。生成CN + NCO和NCCN + (3)O所涉及的所有过渡态都比反应物低得多。因此，新型反应CCN + NO即使在低温下也能有效进行，预计在燃烧和星际过程中都能发挥作用。在CCN + NO和CH + NO反应机理的单重态PESs上发现了显著差异。
