Structural analysis of (R)-3-methylcyclohexanone conformers

The electronic circular dichroism (CD) spectra as a function of temperature for R-(+)-3-methylcyclohexanone (R3MCH) were reported in 11 solvents of wide polarity range for the optically active n → π* transition band. An asymptotic approach on temperature-dependent CD data was utilized to determine conformer’s CD signal and population, in addition to determining enthalpy, entropy, and Gibbs free energy differences between the equatorial and axial conformers. The evaluated thermodynamic constants were compared with values reported in literature and found to be insensitive to solvent polarity. By comparing CD spectra in vapor and solution phases, solvent effects on CD spectra were also investigated and observed to correlate with solvent polarity and nature. Also, DFT calculations of the R3MCH dipole moment components and magnitude for the individual equatorial (EQ) and axial (AX) conformers were performed by employing a hybrid set of type B3LYP with basis set aug-cc-pVTZ and within the framework of the polarizable continuum model. The calculated dipole moment magnitudes of the dominant conformers in different solvents were observed to linearly correlate with solvent polarity.