Knowledge Bank

Measurements of the circular dichroism spectra in the 3-5 $\mu$m region have now been completed for the entire series of molecules $S-(+)-Ph-CHC-X(X=CH3,CH2D,CD2H,CD3).1$ Charge-flow $model2$ calculations of the dipole strengths in the aliphatic CH and CD stretching modes do not depend strongly on the details of the phenyl moiety. In contrast charge-flow model calculations of the corresponding rotational strengths show the importance of including the phenyl group explicitly when interpreting the observed VCD spectra. More specifically, our calculations indicate that electronic charge rearrangement in the phenyl group resulting from aliphatic CH and CD motions contributes significantly to the observed rotational strengths.