Structures of the Optically Active Monofluoro-Substituted Mandelic Acids: Relation to Their Racemic Counterparts and Thermochemical Properties

Sine Larsen, K. Marthi

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Abstract

The crystal structures of the three optically active monofluoro-substituted mandelic acids (C8H7FO3, Mr = 170.14) have been determined from low-temperature X-ray diffraction data. (R)-(-)-ortho-Fluoromandelic acid, monoclinic, P21, a = 8.356(2), b = 10.842(2), c = 8.544(2) Å, β = 94.13(2)°, Z = 4, m.p. 361.8 (5) K. (R)-(-)-meta-Fluoromandelic acid, monoclinic, P21, a = 8.493(3), b = 5.8426(7), c = 15.628 (3) Å, β = 104.10(2)°, Z = 4, m.p. 394.2(5) K. (R)-(-)-para-Fluoromandelic acid, monoclinic, C2, a = 8.464(2), b = 5.8518(13), c = 15.868 (2) Å, β = 107.56(2)°, Z = 4, m.p. 425.8 (5) K. The hydrogen-bonding schemes in these structures have been analysed and compared with the hydrogen-bond patterns in the equivalent racemic acids. The structural data from six other structures were included in the analysis, which led to a general description of the great variety of hydrogen-bond motifs observed in α-hydroxycarboxylic acids. Differences between crystal structures of the racemic and enantiomerically pure fluoromandelic acids have been related to their melting enthalpies. The observed differences in the binary phase diagrams of the three acids can be rationalized in terms of their structural differences.

Original languageEnglish
Pages (from-to)280-292
Number of pages13
JournalActa Crystallographica Section B
Volume53
Issue number2
Publication statusPublished - Apr 1 1997

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Mandelic Acids
thermochemical properties
acids
Acids
Hydrogen bonds
Hydrogen
Crystal structure
hydrogen bonds
crystal structure
Hydrogen Bonding
X-Ray Diffraction
Freezing
Phase diagrams
Enthalpy
Melting
enthalpy
phase diagrams
melting
X ray diffraction

ASJC Scopus subject areas

  • Structural Biology
  • Condensed Matter Physics

Cite this

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title = "Structures of the Optically Active Monofluoro-Substituted Mandelic Acids: Relation to Their Racemic Counterparts and Thermochemical Properties",
abstract = "The crystal structures of the three optically active monofluoro-substituted mandelic acids (C8H7FO3, Mr = 170.14) have been determined from low-temperature X-ray diffraction data. (R)-(-)-ortho-Fluoromandelic acid, monoclinic, P21, a = 8.356(2), b = 10.842(2), c = 8.544(2) {\AA}, β = 94.13(2)°, Z = 4, m.p. 361.8 (5) K. (R)-(-)-meta-Fluoromandelic acid, monoclinic, P21, a = 8.493(3), b = 5.8426(7), c = 15.628 (3) {\AA}, β = 104.10(2)°, Z = 4, m.p. 394.2(5) K. (R)-(-)-para-Fluoromandelic acid, monoclinic, C2, a = 8.464(2), b = 5.8518(13), c = 15.868 (2) {\AA}, β = 107.56(2)°, Z = 4, m.p. 425.8 (5) K. The hydrogen-bonding schemes in these structures have been analysed and compared with the hydrogen-bond patterns in the equivalent racemic acids. The structural data from six other structures were included in the analysis, which led to a general description of the great variety of hydrogen-bond motifs observed in α-hydroxycarboxylic acids. Differences between crystal structures of the racemic and enantiomerically pure fluoromandelic acids have been related to their melting enthalpies. The observed differences in the binary phase diagrams of the three acids can be rationalized in terms of their structural differences.",
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AU - Larsen, Sine

AU - Marthi, K.

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N2 - The crystal structures of the three optically active monofluoro-substituted mandelic acids (C8H7FO3, Mr = 170.14) have been determined from low-temperature X-ray diffraction data. (R)-(-)-ortho-Fluoromandelic acid, monoclinic, P21, a = 8.356(2), b = 10.842(2), c = 8.544(2) Å, β = 94.13(2)°, Z = 4, m.p. 361.8 (5) K. (R)-(-)-meta-Fluoromandelic acid, monoclinic, P21, a = 8.493(3), b = 5.8426(7), c = 15.628 (3) Å, β = 104.10(2)°, Z = 4, m.p. 394.2(5) K. (R)-(-)-para-Fluoromandelic acid, monoclinic, C2, a = 8.464(2), b = 5.8518(13), c = 15.868 (2) Å, β = 107.56(2)°, Z = 4, m.p. 425.8 (5) K. The hydrogen-bonding schemes in these structures have been analysed and compared with the hydrogen-bond patterns in the equivalent racemic acids. The structural data from six other structures were included in the analysis, which led to a general description of the great variety of hydrogen-bond motifs observed in α-hydroxycarboxylic acids. Differences between crystal structures of the racemic and enantiomerically pure fluoromandelic acids have been related to their melting enthalpies. The observed differences in the binary phase diagrams of the three acids can be rationalized in terms of their structural differences.

AB - The crystal structures of the three optically active monofluoro-substituted mandelic acids (C8H7FO3, Mr = 170.14) have been determined from low-temperature X-ray diffraction data. (R)-(-)-ortho-Fluoromandelic acid, monoclinic, P21, a = 8.356(2), b = 10.842(2), c = 8.544(2) Å, β = 94.13(2)°, Z = 4, m.p. 361.8 (5) K. (R)-(-)-meta-Fluoromandelic acid, monoclinic, P21, a = 8.493(3), b = 5.8426(7), c = 15.628 (3) Å, β = 104.10(2)°, Z = 4, m.p. 394.2(5) K. (R)-(-)-para-Fluoromandelic acid, monoclinic, C2, a = 8.464(2), b = 5.8518(13), c = 15.868 (2) Å, β = 107.56(2)°, Z = 4, m.p. 425.8 (5) K. The hydrogen-bonding schemes in these structures have been analysed and compared with the hydrogen-bond patterns in the equivalent racemic acids. The structural data from six other structures were included in the analysis, which led to a general description of the great variety of hydrogen-bond motifs observed in α-hydroxycarboxylic acids. Differences between crystal structures of the racemic and enantiomerically pure fluoromandelic acids have been related to their melting enthalpies. The observed differences in the binary phase diagrams of the three acids can be rationalized in terms of their structural differences.

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