- 作者: 林渭川; 陳振興; 陳立樹; 林心
- 作者服務機構: Department of Chemistry, National Taiwan University
- 中文摘要:
The vicinal H-H coupling constant in the AB2 spectrum, JAB, of 1, 1, 2-trisubstituted ethanes of the type XCH2-CHX2 has been measured in the medium of various solvents and at several different temperatures over the range of 238°-368°K. Based on rotational averaging and on the simple model of internal rotation about the C-C bond, a refiend Karplus equation for the vicinal coupling constant could yield the analytical expression which describes an explicit functional dependence of the vicinal coupling constant on internal rotation parameters, and permits evaluation of ΔE, the energy difference between rotamers, at any fixed temperature.
For neat 1, 1, 2-trichloroethaneΔE was found to keep constant over the range of temperature variation studied, while in the case of neat 1, 1, 2-tribromoethaneΔE increases with increasing temperature in the same temperature range.
In contrast to a small temperature effect a much pronounced medium effect on ΔE was observed for both 1, 1, 2-tribromoethane and 1, 1, 2-trichloroethane. At any fixed temperature ΔE decreases as dielectric constant of the solvent increases. - 英文摘要: --
- 中文關鍵字: --
- 英文關鍵字: --