The anomalously large chiroptical response of (1R,4R)-norbornenone has been probed under complementary vapor-phase and solution-phase conditions to assess the putative roles of environmental perturbations. Measurements of the specific rotation for isolated (gas-phase) molecules could not be reproduced quantitatively by comprehensive quantum-chemical calculations based on density-functional or coupled-cluster levels of linear-response theory, which suggests that higher-order treatments may be needed to accurately predict such intrinsic behavior. A substantial, yet unexpected, dependence of the dispersive optical activity on the nature (phase) of the surrounding medium has been uncovered, with the venerable Lorentz local-field correction reproducing solvent-mediated trends in rotatory dispersion surprisingly well, whereas more modern polarizable continuum models for implicit solvation performed less satisfactorily.
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