Stability of Noble-Gas Molecules and Their SN2 and E2 Reactivity

• Main Author: 周政諺
• Other Authors: 胡維平
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/w75pcu

碩士 === 國立中正大學 === 化學暨生物化學研究所 === 107 === 　　This thesis consists of three chapters. In the first chapter, we designed a class of noble-gas molecules FNgOCH2X (Ng：Xe、Kr), and we study about their stability by using theoretical calculation. The calculation results show that for Ng = Xe, the noble-gas bond energies of these molecules were about 40 kcal/mol, we suggested that these molecules could exist in low temperature. For Ng = Kr, the noble-gas bond energies of these molecules were about 10 kcal/mol, we suggested that these molecules are not stable enough to exist in low temperature. 　　In the second chapter, we used the noble-gas molecule FXeOCH2SH we designed in chapter one to undergo SN2 reaction and study about their reactivity. For this reaction, there will be two reaction pathways. The leaving group can either be FXeO or SH depending on the carbon center the nucleophile attacks. In the current research, we study system with nucleophile as OCl. We found out that whether the leaving group in SH or FXeO, they have the barrier around -2 kcal/mol ~ 2 kcal/mol at the CCSD(T)/CBS level. Then we calculate the rate constants by TST, for the pathway that SH leave, the rate constant is only 3.5 times worse than another pathway. The barrier and rate constant is close enough that we can assume these two pathways can be competitive. 　　In the third chapter, we also used the noble-gas molecule we designed from chapter one to model an epoxidation and study about their reactivity. In this chapter, we were supposed to find an E2 reaction and to study the reactivity between E2 and the SN2 reaction. However, we cannot find a transition state structure for the E2 reaction. We discover a new reaction for having an epoxide as a product. The calculation results show that this reaction is very exothermic, and the barrier is 3 kcal/mol higher then the SN2 reaction at the CCSD(T)/CBS level. From the result of barrier and rate constants, we can suggest that the new reaction we discovered will be the main reaction instead of SN2 reaction at room temperature. Keyword：noble-gas molecules, SN2 reaction, competitive, epoxide