80 kcal mol−1 in the vapour phase, decreasing to 0.47 kcal mol−1 in CCl4 and to −1.25 kcal mol−1 in DMSO. The introduction of a methyl group geminal to the fluorine atom shifts the conformational equilibrium towards the trans rotamer, in contrast to no significant effect when the methyl group is introduced at the α-carbon further from the fluorine atom. Copyright © 2002 John Wiley & Sons, Ltd.
检查了3-
氟-
3-甲基-2-丁酮(
FMB)和
1-氟-3,3-二甲基-2-丁酮(FDMB)的1 H和13 C NMR谱图的溶剂依赖性,并确定了4 J据报道有HF,1 J CF和2 J CF联轴器。使用B3LYP / 6–311 ++ G(2df,2p)级别的密度泛函理论(DFT)和ZPE(零点能量)校正来获得构象几何体。在
FMB和FDMB中,DFT方法仅给出了顺式(F C C O,0°)和反式(F C C O,180°)旋转异构体的两个最小值。假设顺式反式和反式,当通过溶剂化理论分析时,在
FMB中观察到的偶合给出了汽相中的能量差E cis - E trans为3.80 kcal mol -1(1 kcal = 4.184 kJ)(参见DFT值为3.21 kcal mol -1),在CCl 4中降至2.6 kcal mol -1,在
DMSO中降至0.27 kcal mol -1。在FDMB