| Summary: | 碩士 === 中國文化大學 === 化學系應用化學碩士班 === 101 === 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.
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