Acta Crystallographica Section C

Crystal Structure Communications

Volume 65, Part 8 (August 2009)

organic compounds

gz3166 scheme

Acta Cryst. (2009). C65, o388-o395 [ doi:10.1107/S0108270109025141 ]

Enantiotropic phase transition and twinning in 2,2,3,3,4,4-hexafluoropentane-1,5-diol

J.-M. Ha and V. Young

Abstract: Four crystal structure determinations of 2,2,3,3,4,4-hexafluoropentane-1,5-diol (HFPD), C₅H₆F₆O₂, were conducted on a single specimen by varying the temperature. Two polymorphs of HFPD were found to be enantiotropically related as phases (I) and (II), both in the space group P1. These structures contain closely related R₄⁴(20) sheets. A structure determination was completed on form (Ia) at 283 K. Form (Ia) was then supercooled below the phase transition temperature at 279 to 173 K to give form (Ib) for a second structure determination. Metastable form (Ib) was transformed by momentary warming and recooling to give form (II) for a third structure determination at 173 K. Form (II) transformed to form (Ic) upon warming to 283 K. Enantiotropic phase transitions between phases (I) and (II) were confirmed with X-ray powder diffraction and differential scanning calorimetry. Form (Ia) was found as a twin by nonmerohedry by a reflection in (011). This twinning persists in all phases described. Additional twinning was found after the phase (I) to phase (II) transformation. These two additional twin components are related to the first pair by a 180° rotation about the (012) plane. This latter pair of twins persisted as the specimen was warmed back to form (Ic) at 283 K.

Formula: Four forms of C₅H₆F₆O₂


	Structure factor file (CIF format) (84.7 kbytes) [ doi:10.1107/S0108270109025141/gz3166Iasup2.hkl ] Contains datablock Ia

	Structure factor file (CIF format) (83.0 kbytes) [ doi:10.1107/S0108270109025141/gz3166Ibsup3.hkl ] Contains datablock Ib

	Structure factor file (CIF format) (81.4 kbytes) [ doi:10.1107/S0108270109025141/gz3166IIsup4.hkl ] Contains datablock II

	Structure factor file (CIF format) (85.1 kbytes) [ doi:10.1107/S0108270109025141/gz3166Icsup5.hkl ] Contains datablock Ic

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