不對稱1, 2-雙取代乙烷碳-碳單鍵內轉之溫度效應

Effect of Temperature on Internal Rotation about the C-C Bond in Non-Symmetrical 1,2-Disubstituted Ethanes

陳振興(Jenn-Shing Chen) ； 林渭川(Wei-Chuwan Lin)

《化學》 65年1期 (1976/03) Pp. 1-6

https://doi.org/10.6623/chem.1976001

摘要

在不同溫度下測得不對稱1, 2-雙取代乙烷在各種溶劑中所呈現的A_2B_2質子核磁共振譜，所決定的核磁共振實驗參數值列於表一～三。已知乙烷分子內轉能障為3.0 Kcal/mole，吾人可利用以前所導出的不對稱1, 2-雙取代乙烷A_2B-2譜之鄰位偶合參數表示式，來計算當V_1取定值時|L|/A及/或N/A的溫度函數。將|L|/A及/或N/A對溫度作圖，可得對應於各已知V_1值下的等位線。應用這些等位線及|L|/A或N/A在各實驗溫度下的測度可決定V_1值及∆E值。∆E為間型內轉異構體與對型內轉異構體之間的能量差，所決定的∆E值亦列於表一～三。

並列摘要

A_2B_2 proton NMR spectra of some non-symmetrical 1, 2-disubstituted ethanes in the medium of various solvents have been measured at several different temperatures. The determined values of NMR parameters for A_2B_2 spectra were listed in Table 1-3. The previously derived expressions for vicinal coupling parameters in A_2B_2 spectra of non-symmetrical 1,2-disubstltuted ethanes can be used to calculate L/A and/or N/A as a fuction of temperature for each given value of V_1 while assuming V_0 fixed at V_0=3.0 Kcal/mole over the range of temperature variation. A plot of |L|/A vs. temperaturs gives the equipotential contour corresponding to each given value of V_1, and permits evaluation of V_1 and hence ∆E from measurements on either |L|/A or N/A at each experimental temperature. The determined ∆E, the energy difference between gauche and trans rotational isomers, were also listed in Table 1-3.