Theoretical Study of the Reaction Mechanism of HCN+ and CH4 of Relevance to Titan's Ion Chemistry
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- 作者：Yan Li ; Hui-ling Liu ; Xu-ri Huang ; Cai-yun Geng ; Chia-chung Sun ; Au-chin Tang
- 刊名：Journal of Physical Chemistry A
- 出版年：2008
- 出版时间：March 27, 2008
- 年：2008
- 卷：112
- 期：12
- 页码：2693 - 2701
- 全文大小：889K
- 年卷期：v.112,no.12(March 27, 2008)
- ISSN：1520-5215
文摘
Titan is the largest satellite of Saturn. In its atmosphere, CH4 is the most abundant neutral after nitrogen. Inthis paper, the complex doublet potential-energy surface related to the reaction between HCN+ and CH4 isinvestigated at the B3LYP/6-311G(d,p), CCSD(T)/6-311G++(3df,2pd)(single-point), and QCISD/6-311G(d,p) computational levels. A total of seven products are located on the PES. The initial association of HCN+with CH4 is found to be a prereaction complex 1 (HCNHCH3+) without barrier. Starting from 1, the mostfeasible pathway is the direct H-abstraction process (the internal C-H bond dissociation) leading to the productP1 (HCNH++CH3). By C-C addition, prereaction complex 1 can form intermediate 2 (HNCHCH3+) andthen lead to the product P2 (CH3CNH++H). The rate-controlling step of this process is only 25.6 kcal/mol.It makes the Path P2 (1) R 
1 TS1/2 2 TS2/P2 P2 another possible way for the reaction.P3 (HCNCH3+ + H), P5 (cNCHCH2+ + H2), and P6 (NCCH3+ + H2) are exothermic products, but theyhave higher barriers (more than 40.0 kcal/mol); P4 (H + HCN + CH3+) and P7 (H + H2 + HCCNH+)are endothermic products. They should be discovered under different experimental or interstellarconditions. The present study may be helpful for investigating the analogous ion-molecule reaction in Titan'satmosphere.
1 TS1/2 2 TS2/P2 P2 another possible way for the reaction.P3 (HCNCH3+ + H), P5 (cNCHCH2+ + H2), and P6 (NCCH3+ + H2) are exothermic products, but theyhave higher barriers (more than 40.0 kcal/mol); P4 (H + HCN + CH3+) and P7 (H + H2 + HCCNH+)are endothermic products. They should be discovered under different experimental or interstellarconditions. The present study may be helpful for investigating the analogous ion-molecule reaction in Titan'satmosphere.