Study of the mechanism of optical resolutions via diastereoisomeric salt formation: 2. Thermoanalytical and X-ray study of solid solution formation during the resolution of racemic malic acid by R-α-phenylethylamine

D. Kozma, Klára Tomor, C. Novák, G. Pokol, E. Fogassy

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Racemic malic acid (I) was resolved by R-α-phenylethylamine(II). The S-(-)-I.R-(+)-II diastereoisomer was in excess in the precipitated salt. DSC curves and X-ray powder diffracto-grams proved that the diastereoisomeric salt mixture precipitated during the resolution was isomorphous with the optically pure S-(-)-I.R-(+)-II salt. The diastereoisomeric salt mixture containing the R-(-)-I.R-(+)-II salt in abundance bound crystal solvate (water or methanol) when produced by the total evaporation of the mother liquor, while the optically pure R-(-)-I.R-(+)-II salt crystallized without solvate. It is generally assumed that solid solution formation takes place when the two diastereoisomers are alike and the high similarity results in less efficient enantiomer separation. This paper demonstrates that efficient resolution can be accomplished in case of solid solution formation too. The diastereoisomeric salt mixtures can crystallize in isomorphic form even when the physico-chemical properties of the optically pure diastereoisomeric salts are quite different.

Original languageEnglish
Pages (from-to)1613-1623
Number of pages11
JournalJournal of thermal analysis
Volume46
Issue number6
DOIs
Publication statusPublished - Jun 1996

Keywords

  • Optical resolution
  • Racemic malic acid
  • α-phenylethylamine

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Engineering(all)

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