A gas-phase ab initio study of the hydrolysis of HCN
A gas-phase ab initio study of the hydrolysis of HCN
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DOI：
10.1007/s00214-015-1791-7
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发表时间：
2015
影响因子：
1.7
通讯作者：
Futing Xia;P. Ning;Qiulin Zhang;Fenji Li;Gaohong Tao;Kai Tian;X. Huang;Jinhui Peng;Hua Zhu
中科院分区：
文献类型：
--
作者：
Futing Xia;P. Ning;Qiulin Zhang;Fenji Li;Gaohong Tao;Kai Tian;X. Huang;Jinhui Peng;Hua Zhu
HCN的催化水解是目前最有前途的HCN净化方法之一。在6-31++G（d，p）基组下，采用从头算MP2方法，对HCN水解反应的3种反应机理（路径A、B和C）进行了优化，得到了20个过渡态共51个几何构型.它们共享路径A和路径B的水攻击的第一步。在随后的过程中，对于路径A，氧原子的质子首先移动到氮原子，而在路径B中，碳原子的质子首先移动。路径C包含HCN到HNC的结构互变异构体互变，并且被证明是最有利的路径。此外，水辅助水解反应机理进行了检查的三种类型的反应过程。辅助水的引入降低了大部分吉布斯自由能垒，并且甲酰胺是自由能面上最稳定的中间体。w-路径A的吉布斯自由能垒（50.39 kcal/mol）最低。结果表明，H原子从C原子向N原子的转移是反应的速率控制步骤，有效的催化剂应能活化C-N键，促进质子转移。这些信息可能有助于为这一重要反应设计新的催化剂。
The catalyzed hydrolysis of HCN has become one of the most promising methods for the purification of HCN emissions. Three types of reaction mechanisms (named path A, B and C) for HCN hydrolysis were considered, and a total of 51 geometries including 20 transition states were optimized using ab initio MP2 methods with the 6-31++G(d,p) basis set. They share the first step of water attack for path A and B. In the following process, the proton of oxygen atom shifts to the nitrogen atom first for path A, while in path B, the proton of carbon atom shifts first. The path C contains the structural tautomer interconversion from HCN to HNC, and it turns out to be the most favorable pathway. Additionally, the water-assisted hydrolysis reaction mechanisms were examined for the three types of reaction processes. The inclusion of the auxiliary water decreases most of the Gibbs free energy barriers, and the formamide is the most stable intermediate on the free energy surface. The Gibbs free energy barrier of w-path A (50.39 kcal/mol) becomes the lowest. It is found that the process with the transfer of H atom from the C atom to the N atom is the rate-controlling step, and the efficient catalyst should activate C–N bond and assist the proton transfer. This information may help in designing new catalysts for this important reaction.