CAJ | 학술논문

利用双水平直接动力学方法对反应CH_3SH+H的微观机理和动力学性质进行了理论研究.对于此反应的三个反应通道,即-SH和-CH_3基团上的两个氧提取通道及一个取代通道,在MP2/6-311+G(d,p)水平上优化得到了各稳定点的结构及振动频率,并在G3(MP2)水平上进行了单点能量计算以获得更精确的能最信息;在此摹础上运用结合小曲率隧道效应校正的变分过渡念理论(CVT/SCT)计算了各反应通道在220-1000 K温度区间的速率常数.计算结果表明提取-SH基团上H的反应通道R1在整个反应温度区间都是主要通道,而随着温度的升高,低温下的次要反应通道--取代通道R3变得越来越重要,并且在高温下将成为一个竞争的反应通道;提取-CH_3基团上H的反应通道(R2)由于具有较高的反应能垒,因而,其对总反应速率常数的贡献可以忽略.计算得到的总反应速率常数与已有的实验值符合得很好,进而我们预测了该反应在220-1000 K温度范围内速率常数的表达式为:k=5.00×10~(-18)T~(2.39)exp(-119.81/T),为将来的实验研究提供参考.
이용쌍수평직접동역학방법대반응CH_3SH+H적미관궤리화동역학성질진행료이론연구.대우차반응적삼개반응통도,즉-SH화-CH_3기단상적량개양제취통도급일개취대통도,재MP2/6-311+G(d,p)수평상우화득도료각은정점적결구급진동빈솔,병재G3(MP2)수평상진행료단점능량계산이획득경정학적능최신식;재차모출상운용결합소곡솔수도효응교정적변분과도념이론(CVT/SCT)계산료각반응통도재220-1000 K온도구간적속솔상수.계산결과표명제취-SH기단상H적반응통도R1재정개반응온도구간도시주요통도,이수착온도적승고,저온하적차요반응통도--취대통도R3변득월래월중요,병차재고온하장성위일개경쟁적반응통도;제취-CH_3기단상H적반응통도(R2)유우구유교고적반응능루,인이,기대총반응속솔상수적공헌가이홀략.계산득도적총반응속솔상수여이유적실험치부합득흔호,진이아문예측료해반응재220-1000 K온도범위내속솔상수적표체식위:k=5.00×10~(-18)T~(2.39)exp(-119.81/T),위장래적실험연구제공삼고.
We smdied the reaction of CH_3SH+H theoretically using a dual-level direct dynamics method.Three reaction channels:two H-abstraction(from the-SH and-CH_3 groups) and one substitution channels,were found.Optimized geometries,frequencies,and energies of the stationary points as well as extra points along the minimum energy path were calculated at the MP2/6-311+G(d,p)level of theory.The potential energy profiles were then refined by single-point energy calculations at the G3(MP2) level.Furthermore,the rate constants of all three channels were evaluated by canonical variational transition state theory(CVT) with the small-curvature tunneling effect conection(SCT) over the wide temperature range of 220-1000 K These calculations show that H-abstraction from the-SH group(R1)is the major channel for the title reaction over the whole temperature range.The substitution channel(R3)is a minor pathway at low temperatures and becomes more important as the temperature increases.This would be a competitive channel at high temperature while the contribufion of H-abstraction from the-CH_3 group(R2)to the overall rate constant is almost negligible because of its high energy barrier.The calculated CVT/SCT rate constants agree well with the available experimental values.The three-parameter rate-temperature expression for the total reaction over the whole temperature range of 220-1000 K is shown to be k=5.00×10~(-18)T~(2.39)exp(-119.81/T),which may be a useful expression for future experiments.