| 摘要: | 我們使用初始法(ab initio)來研究Isocyanocarbene(HCNC)與NO的反應機構研究。我們使用B3LYP/6-311++G(3df,2p)做結構最佳化，單點能量則使用CCSD(T)/aug-cc-PVQZ//B3LYP/6-311++G(3df,2p)去計算。我們預測並計算所有的結構去找出最適當的路徑，在我們的所有路徑當中，以產生P1(HCNO + CN)與P2(HCN + NCO)兩種產物為主要路徑。P1的路徑，由HCNC和NO先進行加成反應，形成IM2，反應過程放熱-67.83 kcal/mol，接著跨越一個13.41 kcal/mol反應能障(TSiso1)，來形成IM1中間產物，最後IM1直接反應生成最終產物P1(HCNO + CN)，此路徑總放熱為-15.32 kcal/mol。另一條路P2路徑則是由IM2來進行另外一條反應路徑，先跨越一個20.64 kcal/mol的反應能障(TS3)，形成IM7這個五員環結構的中間物，接著進行開環反應，跨越7.37 kcal/mol的反應能障(TS7)，形成IM9，然後斷開C－N鍵，跨過25.23 kcal/mol的能障(TS9)，形成最終產物P2 (HCN + NCO)，此路徑放熱-101.53 kcal/mol。P3的路徑，直接進行加成反應生成IM3，接著經過一個過渡態TS4(Ea = -20.55 kcal/mol)，然後生成最終產物P3(HCN + CNO)，此路徑反應過程放熱為-38.41 kcal/mol。利用Fukui functions以及硬軟酸鹼理論(HSAB)可以用來解釋我們所計算出來的結果。
The mechanisms and kinetics of the reaction of the Isocyanocarbene (HCNC) with the NO have been investigated by ab initio molecular orbital method. The species involved have been optimized at the B3LYP/6-311++G(3df,2p)level and their single-point energies are refined by the CCSD(T)/aug-CC-PVQZ//B3LYP/6-311++G(3df,2p) method. Our calculated results indicate that the favorable pathways for the formation of several isomers of HCNCNO complex. Formations of HCNO + CN (P1), HCN + NCO (P2) and HCN + CNO (P3) are also possible, although these three pathways involve little activation energy.
In the P1 formation, the addition reaction of HCNC plus NO will produce intermediate IM2 firstly with the exothermicity of -67.83 kcal/mol. Then it could overcome a barrier height of 13.41 kcal/mol (TSiso1) to produce IM1. The IM1 will break its CN bond and produce HCNO + CN (P1). However, the IM2 might also pass through a dissociative pathway directly, forming the products of P1, with a relative energy of -15.3 kcal/mol. For the path of P2 formation, the IM2 will proceed another pathway, via the transition state TS3 (Ea = 20.64 kcal/mol), forming five-membered ring intermediate IM7, and then it will open the ring with a barrier height of 7.37 kcal/mol (TS7), forming the intermediate IM9. The IM9 will break its CN bond and pass a barrier height of 25.23kcal/mol (TS9), forming the final products of HCN + NCO (P2), with an overall exothermicity of -101.53 kcal/mol. In the P3 formation, it will firstly form IM3 and then overcome one transition state (TS4, -20.55 kcal/mol), forming the final products of HCN + CNO (P3), with an overall exothermicity of -38.41. kcal/mol. Employing the Fukui function and HSAB theory, we are able to rationalize the scenario of the calculated outcome. |
