Journal of Physical Chemistry B, Vol.102, No.16, 2841-2844, 1998
Enantiomeric differences in ion association in a chiral solvent
Li-7 NMR spectra of solutions of the lithium salts of:the R and S chiral isomers of the sec-butoxycyclooctatetraene dianion (C8H7-OC4H92-) in S,S-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane were found to be remarkably different. The lithium cations in both solutions exist as mixtures of solvent-separated ion pairs and contact ion pairs with the dianion of C8H7-OC4H9. However, the relative concentration of the contact ion pair is much greater for the R isomer of C8H7-OC4H92- than for the S isomer. The complexity of steric interactions involving the chiral solvent and the R and S sec-butoxy groups results in the solvent being much more capable of partially separating Li+ from the S isomer of C8H7-OC4H92- than from the R isomer.
Keywords:HYDROGEN-BOND ASSOCIATION;HOST-GUEST COMPLEXATION;AMINO ESTER SALTS;OPTICAL RESOLUTION;CRYSTAL-STRUCTURE;TRANSITION-STATE;RECOGNITION;CYCLOOCTATETRAENE;CHROMATOGRAPHY;CYCLODEXTRIN