Enantioselective separation of mandelic acid enantiomers by chiral ligand

Based on chiral ligand exchange, the distribution behavior of mandelic acid enantiomers in the two-phase system containing copper iron(II)(Cu(2+)) and N-n-dedecane-L-hydroxyproline (L), was studied. At different pH, the partition of Cu(2+) in the two-phase system containing N-n-dedecane-L-hydroxyproline, was investigated. The formation constant of binary cpmplex(Li(2)Cu) was obtained by regression. The influence of pH, concentrations of Cu(2+) and chiral ligand, and solvents on partition coefficients(K) and separation factor(alpha), was discussed. The experimental results show that Li forms more stable ternary complex with D-mandelic acid than with L- mandelic acid. There is a large influence of pH on K and alpha. At low pH values (<3.5), formation of binary complexes is thermodynamically unfavourable. K and alpha are best when pH values are above 3.5 and the molar ratio of chiral ligand to Cu(2+) is 2:1. At the same time, solvents influence K and alpha very much.