Chiral phase partitioning by enantioselective complexation: Characterisation by the semi-empirical application of regular solution theory
✍ Scribed by Paul J. Pickering; Julian B. Chaudhuri
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 130 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0899-0042
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✦ Synopsis
The thermodynamics underlying enantioselective complexation and partitioning behaviour are poorly understood. This paper presents a model that decouples the effects of enantioselective complexation and subsequent diastereomer partitioning. Regular solution theory is applied in a semi-empirical manner to describe the diastereomer partitioning process, which is reported to be governed by hydrophobic interactions. The model was shown to give a good fit to experimental partitioning for the enantioselective extraction of phenylalanine isomers by two chiral extractants; a modified amino acid [copper (II) N-decyl-(L)-hydroxyproline] and a chiral crown ether [(S)bis(phenylnaphtho)-20-crown-6]. A variety of aliphatic and aromatic solvents were tested. The predicted and observed experimental enantioselectivities were found to vary exponentially with the difference in the solubility parameters of the aqueous and organic phases and with those of the two diastereomeric complexes formed. This model provides the basis for a better understanding of enantioselective partitioning effects.