Journal of the American Chemical Society 2003-12-24

Optical rotation of noncovalent aggregates.

Michael-Rock Goldsmith, Nilu Jayasuriya, David N Beratan, Peter Wipf

Index: J. Am. Chem. Soc. 125(51) , 15696-7, (2003)

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Abstract

Dilute solutions of (R)-(-)-pantolactone in CCl4 were studied by polarimetry in conjunction with theoretical calculations of [alpha]D. Our data demonstrate that the self-association of a chiral solute results in a change in [alpha]D that can be accounted for by the presence of hydrogen-bonded dimeric species. The theoretical analysis predicts a concentration-dependent specific rotation in good agreement with experiment. Further exploration of monomer and dimer [alpha]D differences, through atomic map analysis, reveals large contributions to [alpha]D from the hydrogen-bonded hydroxyl groups in the tightly-coupled dimer. This study extends the computation of chiroptical properties to the accurate concentration-dependent prediction of [alpha]D for noncovalently interacting self-associating species.