FACTORS INFLUENCING ENANTIOMERIC RECOGNITION OF PRIMARY ALKYLAMMONIUMSALTS BY PYRIDINO-18-CROWN-6 TYPE LIGANDS

Equilibrium constant (K), enthalpy change (DELTAH), and entropy change (DELTAS) values were determined for the interactions of a series of c hiral pyridino-18-crown-6 type ligands with enantiomers of several pri mary alkylammonium salts in various solvents. Good enantiomeric recogn ition in terms of DELTA log K was observed in many systems with DELTA log K values greater than 0.4. The extent of enantiomeric recognition and the stabilities of the chiral crown ether-ammonium salt complexes were found to depend on the rigidity of the macrocyclic frame of the l igand, the type and arrangement of the donor atoms on the ligand, the bulkiness of the substituents on the ligand's chiral centers, the loca tion of the chiral centers on the ligand, and the solvent. The effects of these factors on the extent of enantiomeric recognition and on the stabilities of the complexes were examined for the systems studied.