Experimental determination of the conformational free energies (A values) of fluorinated substituents in cyclohexane by dynamic 19F NMR spectroscopy. Part 2. Extension to fluoromethyl, difluoromethyl, pentafluoroethyl, trifluoromethylthio and trifluoromethoxy groups
作者:Yvan Carcenac、Marc Tordeux、Claude Wakselman、Patrick Diter
DOI:10.1039/b516641a
日期:——
The synthesis of monosubstituted and 1,4-substituted cyclohexanes bearing one of the title groups is described. The conformational analysis of these compounds was studied by 19F NMR spectroscopy at various temperatures. Chemical shifts for each conformer above the coalescence temperature were obtained by binomial regression from low temperature values, allowing the high precision determination of the
描述了带有标题基团之一的单取代和1,4-取代的环己烷的合成。通过在不同温度下的19 F NMR光谱研究了这些化合物的构象分析。通过从低温值进行二项式回归,获得了高于聚结温度的每个构象异构体的化学位移,从而可以高精度确定平衡常数以及氟化物的相应热力学参数(ΔG °,ΔH °,ΔS °)取代基。对于甲值(-Δ ģ ° 298K),以下平均获得数据:1.59(CFH 2),1.85(CF 2H),2.67(C 2 F 5),0.79(OCF 3)和1.18(SCF 3)[以kcal mol -1表示]。