Co-crystal of (R,R)-1,2-cyclohexanediol with (R,R)-tartaric acid, a key structure in resolution of the (±)-trans-diol by supercritical extraction, and the related ternary phase system

Paul Thorey, Petra Bombicz, Imre Miklós Szilágyi, Péter Molnár, György Bánsághi, Edit Székely, Béla Simándi, László Párkányi, György Pokol, János Madarász

Research output: Article

25 Citations (Scopus)

Abstract

A novel co-crystal of trans-(R,R)-1,2-cyclohexanediol and (R,R)-tartaric acid (with 1:1 molar ratio, 1) has been found to be a key crystalline compound in the improved resolution of (±)-trans-1,2-cyclohexanediol by supercritical fluid extraction. The molecular and crystal structure of this co-crystal, which crystallizes in orthorhombic crystal system (space group P212121, a = 6.7033(13) Å, b = 7.2643(16), c = 24.863(5), Z = 4), has been solved by single crystal X-ray diffraction (R = 0.064). The packing arrangement consists of two dimensional layers of sandwich-like sheets, where the inner part is constructed by double layers of tartaric acids which hydrophilicity is "covered" on both upper and bottom side by cyclohexanediols with the hydrophobic cyclohexane rings pointing outward. Thus, a rather complex hydrogen bonding pattern is constructed. The relatively high melting point (133 °C) observed by both simultaneous TG/DTA and DSC, and the main features of FTIR-spectrum of 1 are explained by the increased stability of this crystal structure. DSC studies on binary mixtures of co-crystal 1 with (R,R)-1,2-cyclohexanediol or (R,R)-tartaric acid, revealed eutectic temperatures of Teu = 100 or 131 °C, respectively. Between (S,S)-1,2-cyclohexanediol and (R,R)-tartaric acid a eutectic temperature of Teu = 85 °C have also been observed. The phase relations have been confirmed by powder X-ray diffraction, as well.

Original languageEnglish
Pages (from-to)129-136
Number of pages8
JournalThermochimica Acta
Volume497
Issue number1-2
DOIs
Publication statusPublished - jan. 10 2010

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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