Innovative Fiber-optical Sensing (InFaSe)
Synthesis and NMR spectroscopic conformational
Synthesis and NMR spectroscopic conformational analysis of bencoic acid esters of mono- and 1,4-dihydroxycyclohexane, 4-hydroxycyclohexanone and the -ene analoque - The more polar the molecule the more stable the axial conformer
E. Kleinpeter, P. Werner, T. Linker
para-Substituted benzoic acid esters of cyclohexanol, 1,4-dihydroxycyclohexane, 4-hydroxy cyclohexanone and of the corresponding exo-methylene derivative were synthesized and the conformational equilibria of the cyclohexane skeleton studied by low temperature ¹H and ¹³C NMR spectroscopy. The geometry optimized structures of the axial/equatorial chair conformers were computed at the DFT level of theory. Only one preferred conformation of the ester group was obtained for both the axial and the equatorial conformer, respectively. The content of the axial conformer increases with growing polarity of the 6-membered ring moiety; hereby, in addition, the effect of sp² hybridization/polarity of C(4)=O/C(4)=CH2 on the present conformational equilibria is critically evaluated. Another dynamic process could be studied, for the first time in this kind of compounds.
Journal Article