Rotamer populations in 9-(alkoxymethyl)-1,4-dimethyltriptycenes, where the alkyl is an ethyl, a methyl, or a 2,2,2-trifluoroethyl, were examined by 1H NMR spectra. The populations of the sc isomer decreased as the alkyl group becomes electronegative. The population ratio, sc/ap, of the methyl compound was almost the same with that for 1,4-dimethyl-9-(phenoxymethyl)triptycene to indicate that the populations of the rotamers in this and related series of compounds are determined on a delicate balance of various factors such as van der Waals repulsive and charge-transfer attractive interactions.
通过 1 H NMR 谱检查了 9-(烷氧基甲基)-1,4-二甲基
三蝶烯中的旋转异构体群,其中烷基是乙基、甲基或
2,2,2-三氟乙基。随着烷基变得带负电,sc 异构体的数量减少。甲基化合物的群体比 sc/ap 与 1,4-二甲基-9-(苯氧基甲基)
三蝶烯的群体比几乎相同,表明该化合物和相关系列化合物中的旋转异构体的群体是根据各种因素的微妙平衡,例如范德华排斥力和电荷转移吸引相互作用。