The Pfeiffer Effect with Cinchoninium Ion as a Chiral Environment Substance

The Pfeiffer effect of tris(oxalato)chromate(III) was examined and compared with that of tris(1, 10-phenanthroline)cobalt(II) by using cinchoninium ion and some of its related chiral compounds as an environment substance in water as well as in several mixed solvents with water. It was proposed that [Cr(ox)3]3- ion attacks the environment substance through electrostatic interaction and is subject to the asymmetry around the C-8 atom of cinchoninium ion, while [Co(phen)3]2+ ion associates with cinchoninium ion through the hydrophobic interaction with the quinolyl group and is subject to the asymmetry around the C-9 atom. The rate of appearance of the Pfeiffer effect was also measured for the [Cr(ox)3]3- system. It was found that the inversion rate of one enantiomer enriched by the Pfeiffer effect is appreciably retarded by cinchoninium ion, while the other enantiomer is kinetically little affected by it. The same will hold for the corresponding [Co(phen)3]2+ system.