HNCO与CX（X=F，Cl，Br）自由基反应机理的密度泛函理论研究

用量子化学密度泛函理论的B3LYP方法，在6-31+G~*水平上按BERNY能量梯度解 析全参数优化了HNCO与CX（X=F，Cl，Br）反应势能面上各驻点的几何构型，通过 振动频率分析确认了中间体和过渡态，内禀反应坐标（IRC）对反应物、中间体、 过渡态和产物的相关性予以证实，对各驻点进行了零点能校正（ZPE）在此基础上 计算了反应能垒。研究结果表明，与HNCO和其它小分子自由基反应不同，HNCO与 CX自由基反应首先发生分子间H原子迁移，随后N与CX的C（1）原子相互靠近成键并 生成较稳定的中间体，再发生N-C（2）键的断裂，完成N向C（1）上的迁移并进一 步解离为产物。反应按反应物→TS1→IM→TS2→产物通道进行。反应为放热反应。

Density Functional Theory Study on the Mechanism for the Reaction of HNCO with CX (X = F, Cl, Br) Radical

The reaction mechanisms of HNCO with CX (X = F, Cl, Br) have been investigated using density functional theory (DFT) at the B3LYP/6- 31+G~* level. The transition states and intermediates of these reactions are verified by frequency analysis. The relationship of reactants, transition states, intermediates and products is affirmed by IRC. The energy barriers of these reactions have also been calculated. The results show that reactions of HNCO with CX are different from reactions of HNCO with other small molecular radicals. The hydrogen transfer between molecules is the first step in the case of HNCO with CX reactions. Then the N atom approaches the C(1) atom forming the N-C(1) bond and the stable intermediate (IM) is obtained. After that the N atom transfers to C(1) forming TS2. The TS2 decomposes into product finally. The reaction pathway is reactants→ TS1→IM→TS2→products. These reactions are exothermic.