1,2－雙取代乙烷分子內轉之核磁共振研究

NMR Studies on Internal Rotation in Some l, 2-Disubstituted Ethanes

陳立樹(Li-Shu Chen) ； 林渭川(Wei-Chuwan Lin)

《化學》 61年4期 (1972/12) Pp. 141-148

https://doi.org/10.6623/chem.1972019

摘要

1-溴-2-氯乙烷，3-氯丙酸乙酯及3-甲氧基丙睛之質子磁共振譜之譜圖受到溶劑之影響至巨，本文述其在五至十種溶劑中譜圖之變化，並由其譜圖所測得之鄰位偶合參數，進而求得在各種溶劑中之最高內轉能障及內轉異構體間之位能差。1-溴-2-氯乙烷在各種溶劑中以對位型內轉異構體較爲穩定，3-氯丙酸乙酯在環乙烷及四氯化碳中，其對位型與間位型內轉異構體有相同之穩定度，在介電常數大於氯仿之溶劑中以間位型內轉異構體較爲穩定。3-甲氧基丙睛在氯仿及二氯甲烷中，其對位型與間位型內轉異構體有相同之穩定度，在介電常數大於丙酮之溶劑中則以間位型內轉異構體較爲穩定。

並列摘要

The A_2B_2, system of PMR spectra of 1-bromo-2-chloroethane, ethyl 3-chloropropionate, and 3-methoxypropionitrile exhibit appreciable solvent effect at room temperature. NMR spectroscopic parameters of A_2B_2 spectrum as well as physical parameters related to internal rotation, i.e. the highest energy barrier and the energy difference between rotamers, were determined for these compounds in the medium of various solvents. It was found that in the case of 1-bromo-2-chloroethane, the trans rotamer is more stable than the gauche rotamers, and the energy difference decreases with increasing dielectric constant of solvent. While in the case of ethyl 3-chloropropionate and 3-methoxypropionitrile, both trans and gauche rotamers are equally stable in a solvent of low dielectric constant, however in a solvent of higher dielectric constant the gauche rotamers become more stable than the trans rotamer and the energy difference becomes increasingly more pronounced with increasing dielectric constant of solvent.