Stereochemical dependence of 3J CH coupling constants in 2-substituted 4-t-butyl-cyclohexanone and their alcohol derivatives

Abstract

Theoretical and experimental studies on 3J C2H6eq NMR spin - spin coupling constants in both the 2-X-4-t-butyl-cyclohexanone (X = H, CH 3, F, Cl, and Br) and in their alcohol derivatives series are reported. Results thus found are rationalized in terms of the transmission of the Fermi contact contribution to such couplings. To this end, dependencies of 3J C2H6eq couplings versus the C 2 - C 1 - C 6 angle are compared in both series for equatorial and axial X orientations. The main trend is described in terms of the rear lobes interaction. Besides, for X = halogen atom in equatorial orientation a rather strong interaction between oxygen and halogen lone pairs is observed, and its influence on 3J C2H6eq couplings is discussed and rationalized in terms of different Fermi contact transmission pathways. (Figure presented) © 2011 American Chemical Society.