Fluorine deshielding in the proximity of a methyl group. An experimental and theoretical study
作者:Gordon W. Gribble、Daniel J. Keavy、Erik R. Olson、Ian D. Rae、Alfred Staffa、Tomas E. Herr、Marta B. Ferraro、Rubén H. Contreras
DOI:10.1002/mrc.1260290504
日期:1991.5
19F chemical shifts are reported for a series of alkyl‐substituted fluoronaphthalenes and related compounds that exhibit steric crowding around the fluorine atom due to the proximity of methyl groups. Comparisons of these chemical shifts with others measured in similar compounds but without the corresponding methyl groups show that this crowding effect produces a large low‐field shift of the 19F signal
报道了一系列烷基取代的氟萘和相关化合物的 19F 化学位移,这些化合物由于靠近甲基而在氟原子周围表现出空间拥挤。这些化学位移与在没有相应甲基的类似化合物中测量的其他化学位移的比较表明,这种拥挤效应产生了 19F 信号的大低场位移。最近报道了 17O 化学位移的类似效果,但对空间拥挤的敏感性更高。这种邻近效应对 19F 化学位移的电子起源在分子轨道理论中在 INDO 水平上使用极化传播器技术的内部投影进行了分析。