CH2SH与NO2双自由基反应机理的理论研究

在B3LYP/6-311＋＋G(2df,p)水平上优化了标题反应驻点物种的几何构型, 并在相同水平上通过频率计算和内禀反应坐标(IRC)分析对过渡态结构及连接性进行了验证. 采用双水平计算方法HL//B3LYP/6-311＋＋G(2df,p)对所有驻点及部分选择点进行了单点能校正, 构建了CH2SH＋NO2反应体系的单重态反应势能剖面. 研究结果表明, CH2SH与NO2反应体系存在4条主要反应通道, 两个自由基中的C与N首先进行单重态耦合, 形成稳定的中间体HSCH2NO2 (a). 中间体a经过C—N键断裂和H(1)—O(2)形成过程生成主要产物P1 (CH2S＋trans-HONO), 此过程需克服124.1 kJ•mol－1的能垒. 中间体a也可以经过C—N键断裂及C—O键形成转化为中间体HSCH2ONO (b), 此过程的能垒高达238.34 kJ•mol－1. b再经过一系列的重排异构转化得到产物P2 (CH2S＋cis-HONO), P3 (CH2S＋HNO2)和P4 (SCH2OH＋NO). 所有通道均为放热反应, 反应能分别为－150.37, －148.53, －114.42和－131.56 kJ•mol－1. 标题反应主通道R→a→TSa/P1→P1的表观活化能为－91.82 kJ•mol－1, 此通道在200～3000 K温度区间内表观反应速率常数三参数表达式为kCVT/SCT＝8.3×10－40T4.4 exp(12789.3/T) cm3•molecule－1•s－1.

Theoretical Study on the Biradical Reaction Mechanism of CH2SH with NO2

The mechanism for the reaction CH2SH with NO2 was investigated at the HL//B3LYP/6-311＋＋G(2df,p) level on single potential energy surface. All stationary points involved in the title reaction were calculated at the B3LYP/6-311＋＋G(2df,p) level. Frequency calculation and intrinsic reaction coordinate (IRC) analysis at the same level were applied to validation of the connection of transition states. The results show that CH2SH＋NO2 system has four dominating reaction channels. Firstly, CH2SH and NO2 take the carbon-to-nitrogen approach forming an adduct HSCH2NO2 (a), followed by C—N bond rupture along with H(1)—O(2) bond formation leading to the major product P1 (CH2S＋trans-HONO). This process with a barrier height of 124.1 kJ•mol－1. HSCH2NO2 (a) can undergo the C—O bond formation along with C—N bond rupture to HSCH2ONO (b), and the barrier height is exceedingly high, 238.34 kJ•mol－1. b will take subsequent conversion and dissociation to products P2 (CH2S＋cis-HONO), P3 (CH2S＋HNO2) and P4 (SCH2OH＋NO). All the channels are exothermic reactions and the reaction energy of generation is －150.37, －148.53, －114.42 and －131.56 kJ•mol－1, respectively. The channel R→a→TSa/P1→P1 is the major channel for the reaction of CH2SH with NO2. Apparent activation energy for the major channel is －91.82 kJ•mol－1. The fitted three-parameter expression for the major channel (R→a→TSa/P1→P1) is kCVT/SCT＝8.3×10－40T4.4exp(12789.3/T) in the temperature range of 200～3000 K, in which k takes unit of cm3•molecule－1•s－1.