NMR spectroscopic conformational analysis of 4-methylene-cyclohexyl pivalate-The effect of sp2 hybridization.

The conformational equilibrium of the axial/equatorial conformers of 4-methylene-cyclohexyl pivalate is studied by dynamic NMR spectroscopy in a methylene chloride/freon mixture. At 153 K, the ring interconversion gets slow on the nuclear magnetic resonance timescale, the conformational equilibrium (-ΔG°) can be examined, and the barrier to ring interconversion (ΔG# ) can be determined. The structural influence of sp2 hybridization on both ΔG° and ΔG# of the cyclohexyl moiety can be quantified.