RESUMO
Structural knowledge of the high-temperature phases of saturated carboxylic acids (C(n)H(2n-1)O(2)H) from C(6)H(11)O(2)H to C(23)H(45)O(2)H is now complete. Crystal structures of the high-temperature phases of even acids from decanoic (C(10)H(19)O(2)H) to eicosanoic (C(20)H(39)O(2)H) are reported. The crystal structures of the six compounds were determined from powder X-ray diffraction data following direct space methods and refined by the Rietveld method combined with force field geometry optimization. The combination proved to be a valuable approach to obtain structures that are chemically sensible and in close agreement with the powder pattern. At the end of the process solid-state DFT calculations were applied to improve the overall accuracy of the system but in this case DFT did not render better structures. The high-temperature solid phases of even carboxylic acids are all P2(1)/c with Z=4, the molecules are united into dimers via strong hydrogen bonds. Two major types of interactions govern the crystal packing of carboxylic acids, hydrogen bonds and van der Waals interactions. A survey of the intermolecular interactions has revealed that hydrogen bonds are the dominant interaction for acids with less than 23 carbon atoms in the alkyl chain while van der Waals interactions dominate the packing for acids with more than 23 carbon atoms.
RESUMO
In the crystal structure of the title compound, C16H32O2, the molecules are arranged into dimers through O-H...O hydrogen bonds. These dimers are packed in bilayers with terminal methyl groups at both external faces, and these layers are parallel to the crystallographic (100) plane. All C-C bonds of the alkyl chain show an antiperiplanar (trans) conformation, with slight deviations from the ideal value in the C-C bonds close to the intermolecular hydrogen bonds. The similarity between the carboxyl C-O bond distances is consistent with the existence of cis-trans tautomerism.