Crystallization of stable and metastable phases of phenylsuccinic acid
2006 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 6, no 5, 1143-1153 p.Article in journal (Refereed) Published
In the crystallization of a racemic mixture, formation of a conglomerate, i.e., a mechanical Mixture of enantiomerically pure crystals, is the basic requirement for separation of enantiomers by preferential crystallization. Phenylsuccinic acid (PSA) is in the literature reported as a system forming a racemic compound, i.e., each crystal is an ordered mixture of the two enantiomers. In the present work, the properties of PSA were explored, with the underlying ambition of finding a conglomerate. Racemic PSA was crystallized by unseeded batch cooling crystallization in water, in acetic acid, and in 2-propanol (IPA). The corresponding data on solubility and the metastable limits were determined. Crystallization of racemic PSA in seven different solvents generated racemic PSA solvates with 2-propanol and with dioxane, respectively. The solubility of the (RS)-PSA.IPA solvate was determined, and the transition temperature between the solvated and the ansolvate (RS)-PSA I was found to be 16.5 degrees C. In addition to the solution crystallization investigation, an extensive thermal analysis of the racemate and of pure (S)-PSA was performed. A metastable racemate was produced by melt crystallization but was never obtained in Solution crystallization, although unusually high cooling rates combined with different levels of concentration and stirring conditions were used. Throughout this work, the solution concentration and the crystal modification type obtained upon nucleation were determined by in situ ATR-FTIR spectroscopy coupled with multivariate Partial Lease Squares (PLS) calibrations. The work suggests that for a system reported to be forming a racemic compound, there are at least three opportunities to find a conglomerate that should be explored: (i) a conglomerate that may be the stable modification at a different higher or lower temperature; (ii) a metastable conglomerate that may have a sufficient stability for a separation to be performed; (iii) a solvated conglomerate, either more or less stable than the ansolvate.
Place, publisher, year, edition, pages
2006. Vol. 6, no 5, 1143-1153 p.
(rs)-phenylsuccinic acid, organic-compounds, crystal packing, mandelic-acid, stability
IdentifiersURN: urn:nbn:se:kth:diva-15661DOI: 10.1021/cg050089qISI: 000237420100018ScopusID: 2-s2.0-33744734665OAI: oai:DiVA.org:kth-15661DiVA: diva2:333703
QC 201005252010-08-052010-08-05Bibliographically approved