ENANTIOMERIC DIFFERENCES IN ION ASSOCIATION IN A CHIRAL SOLVENT

Li-7 NMR spectra of solutions of the lithium salts of:the R and S chir al isomers of the sec-butoxycyclooctatetraene dianion (C8H7-OC4H92-) i n S,S-(+)-2,3-dimethoxy-1,4-bis(dimethylamino)butane were found to be remarkably different. The lithium cations in both solutions exist as m ixtures of solvent-separated ion pairs and contact ion pairs with the dianion of C8H7-OC4H9. However, the relative concentration of the cont act ion pair is much greater for the R isomer of C8H7-OC4H92- than for the S isomer. The complexity of steric interactions involving the chi ral solvent and the R and S sec-butoxy groups results in the solvent b eing much more capable of partially separating Li+ from the S isomer o f C8H7-OC4H92- than from the R isomer.