单分子水对CH_2SH+NO_2反应机理影响的理论研究

Theoretical studies on the single water molecule-assisted reaction of CH_2SH with NO_2

在B3LYP/6-311++G(2df,p)水平下对单分子水参与下的CH_2SH+NO_2反应的微观机理进行了研究.为了获得更准确的能量信息,采用HL复合方法和CCSD(T)/aug-ccpvtz方法进行单点能校正.结果表明,加入单分子水后的CH_2SH+NO_2反应体系,共经过10条不同的反应路径,得到6种反应产物.与裸反应(CH_2SH+NO_2)相比,水分子在反应中起到了明显的正催化作用.不仅使生成产物trans-HONO的能垒(-52.84kJ·mol^(-1))降低了176.94kJ·mol^(-1),而且不需经过复杂的重排和异构化过程便可得到产物cis-HONO.在生成产物cis-HONO通道(Path3和Path4)中,活化能垒分别为143.65和126.70kJ·mol^(-1),而其裸反应的活化能垒却高达238.34kJ·mol^(-1).生成HNO_2的通道中(Path5和Path6)活化能垒分别为295.23和-42.19kJ·mol^(-1).其中Path6的无势垒过程使HNO_2也成为该反应的主要产物.另外,单分子水还可通过氢迁移的方式直接参与CH_2SH+NO_2的反应,活化能垒(TS7-TS10)分别为-10.62,151.03,186.22和155.10kJ·mol^(-1).除直接抽氢通道中的(Path8-Path10)外,其余反应通道均为放热反应,在热力学上是可行的.

The reaction mechanism of the CH2 SH＋NO2 in the presence of water has been investigated theoretically for the first time using the HL and CCSD（T）/aug-cc-pvtz methods. The goal of the pres- ent investigation is to determine how the single water molecule can affect the reaction mechanisms and estimate the importance of water effects on the CHzSH q-NO2 reaction. Single point energies were performed using the HL method at the B3LYP/6-311＋＋G（2df, p） optimized geometries. Our theo- retical results indicate that there are ten reaction pathways and corresponding six products. The single water molecule in the CH2 SH ＋NO2 reaction has a remarkable positive influence on reducing the reac- tion barrier by comparison with CH2SH -l-NO2 reaction. Not only did the reduce the reaction barrier for the formation of trans-HONO but also didn＇t go through rearrangement and isomerization in the case of obtaining the product cis-HONO. The barriers of the reaction path 3 and path 4 are 143.65, 126.70 kJ · mol^-1 ,respectively,whereas the barrier of the CH2SH＋NO2 in the absence of water reac- tion is exceedingly high,238.34 kJ · mol-1 for the formation of cis-HONO. The barriers of the path 5 and path 6 processes are 295.23 and --42.19 kJ· mol^-1 ,respectively,among non barrier process for the path 6. In addition,the single water molecule react with CH2SH ＋NO2 by the way of hydrogen migration. The barriers of the reaction path 7-10 are -10.62,151.03,186.22,155.10 kJ · mol^-1 ,re- spectively. It is feasible in the thermodynamics and the paths are exothermic reactions except Path8- 10.