Low-temperature 13C n.m.r. spectra allowed the observation of two different groups of signals, corresponding to the O,O-anti- and O,O-syn-rotamers, of a number of 2-acylfurans with the following alkyl groups bonded to carbonyl: Me, Et, Pri, But, pentan-3-yl. The ratios of these rotamers in dimethyl ether were thus obtained, and the barriers for the syn-anti interconversion were found to decrease with
低温13 C NMR谱允许的信号的两个不同组的观察,对应于O,O-抗-和O,O-顺-rotamers,一些2- acylfurans与烷基键合至羰基的以下:ME等,
镨我,卜吨,戊-3-基。由此获得了这些旋转异构体在二
甲醚中的比例,并且发现随着烷基的体积的增加,用于顺-反互转换的障碍减小。虽然分开13对于相应的2-酰基
噻吩的旋转异构体,未检测到C信号,但是线增宽效应允许测量互转换垒。
镧系元素对后一种衍
生物(在1 H和13 C频率下)进行的位移实验表明,在所有所研究的2-酰基
噻吩中,S,O-合成旋转异构体占主导地位。