理論計算探討教(1)HFCO+nH2O(n=1,2)之反應機構(2)N-H鍵活化反應機構:Ni(0)+NH3->NiNH+H2

• Main Author: 蔡武宏
• Other Authors: 何嘉仁
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/6c4m48

博士 === 國立臺灣師範大學 === 化學系 === 96 === There are three major themes in this thesis. I. A theoretical study on the reaction pathways of HFCO + H2O The optimized structure and harmonic frequencies for the intermediates, transition states and product complex on the ground state potential energy surfaces of the reaction formal fluoride with water, including catalytic pathway, concerted and stepwise hydrolysis pathways, were characterized at the molecular orbital theory MP2/6-311++G(d,p) level. Theoretical method was employed to calculate the corresponding energies with the zero-point energy corrections by the MP2/6-311++G(d,p) approach. The catalytic reaction, which is formyl fluoride follow dissociation pathway to yield HF and CO, was computed to be the lowest barrier with 29.6 kcal/mol. And the product complex is the most stable in this study. The concerted hydrolysis pathway has smaller barriers 33.0 kcal/mol than the stepwise one. The stepwise hydrolysis pathway has the highest barrier, 42.1 kcal/mol, in this work. II. Calculated reaction mechanism of HFCO + 2H2O The ab initio MP2/6-311++G(d,p) theoretical method was employed to study the mechanism of reaction of HFCO with 2 molecular H2O in gas phase. Three reaction pathways, the catalytic, concerted hydrolytic and the stepwise hydrolytic pathways were considered. The result shows that the catalytic pathway has the lowest barrier of 24.9 kcal/mol, with the product complex being the most stable on the potential energy profile in this study. H2O molecule provides two functions in the hydrolysis reaction, one acts as a nucleophile, the other as a catalyst. The two active barriers of hydrolysis pathways are without significant difference. However, the barrier of the stepwise one, 29.7 kcal/mol, is a little smaller than the concerted counterpart, 30.6 kcal/mol. III. N-H bond activation: Ni (0) + NH3 à NiNH + H2. A DFT study The reaction between Ni (d10, 1S, and s1d9, 3D) and NH3 have been carried out at the B3PW91/6-311++G(3df,2p) theoretical levels. The intermediates in the reaction pathway transfering from one to another via specific transition state is rationalized by their structures and Wiberg bond indices. The reaction of Ni (singlet and triplet ) + NH3 à NiNH + H2 is predicated to be endothermic (10.61 kcal/mol for singlet and 36.99 kcal/mol for triplet).