Ranking the effect of [1A(ax), 1B(eq)] versus [1A(eq), 1B(ax)] cyclohexane ring substitution on the 1H chemical shifts of γ-methylene cyclohexane ring protons using 2,2-disubstituted adamantanes as models

Abstract

When two different substituents are placed in the nonbridgehead position of adamantane, the two [1A(ax), 1B(eq)] and [1A(eq), 1B(ax)] cyclohexane chair conformers are modeled and features of their NMR spectra can be studied from a single spectrum at 298 K. The effect of [1A(ax), 1B(eq)] and [1A(eq), 1B(ax)] cyclohexane ring substitution on the 1H resonance separation within the γ-CH 2s of cyclohexane ring is compared for various substituent pairs; this aim is approached by measuring the 1H chemical shift separation within the 4′,9′-H and 8′,10′-H methylenes from the 1H NMR spectrum of the model 2A,2B-disubstituted adamantane at 298 K.