Spatial substituent effects of various fluorinated groups on the 13C chemical shifts in cyclohexanes

Abstract

The effect of introduction of fluorinated groups (CH(2)F, CHF(2), CF(3), C(2)F(5), OCF(3), SCF(3)) on the (13)C NMR chemical shifts in cyclohexanes is examined. The two main effects are caused by location at the alpha and gamma carbon positions. Comparison of the various data allowed the calculation of increments corresponding to the introduction of fluorinated groups at axial or equatorial positions on the cyclohexane ring. The introduction of fluorine atoms in methoxy and thiomethoxy groups has only a slight effect through the heteroatom on the (13)C chemical shifts.