Optical Rotary Dispersion Studies. 129. Conformational Isotope Effects and Octant Contributions of CD3 and 13CH3 Groups in Cyclohexanone

Article abstract of DOI:10.1021/ja00534a035

Through the variable-temperature circular dichroism measurements of (2S)-2-methyl-d₃-2-methylcyclohexanone (3) and (2S)-2-methyl-13C-2-methylcyclohexanone (4), quantitative values for the conformational isotope effect are obtained.The chair conformation with the heavier isotope in the equatorial position is found to be energetically preferred by 3.4 and 1.5 cal/mol for 3 and 4, respectively, and empirical force-field calculations qualitatively confirm this view.The CD3 and 13CH3 groups act as weaker octant perturbers compared to CH3.