The 400 MHz 1H NMR spectrum of the title compound at −100 °C in dichloromethane revealed the presence of two isomers in a ratio of 88 : 12, which results from restricted rotation about the triptycyl–oxygen single bond. The major isomer was assigned to the ap rotamer on the basis of the low temperature 13C NMR spectrum. Dynamic NMR studies gave the activation parameters for the ap→±sc conversion: ΔH\eweq=11.9±0.5 kcal/mol (1 calth=4.184 J), ΔS\eweq=2.6±2.5 eu, ΔG\eweq200K=11.4 kcal/mol. Results of molecular mechanics calculations on the compound are discussed.
标题化合物在-100 °C 在
二氯甲烷中的 400
MHz 1H NMR 谱表明存在两种异构体,比例为 88:12,这是由于三蝶酰基-氧单键的旋转受限所致。根据低温 13C NMR 谱将主要异构体指定为适体异构体。动态NMR研究给出了ap→±sc转化的活化参数:ΔH\eweq=11.9±0.5 kcal/mol (1 calth=4.184 J), ΔS\eweq=2.6±2.5 eu, ΔG\eweq200K=11.4 kcal/mol 。讨论了该化合物的分子力学计算结果。