Uric Acid Dihydrate Revisited

Parkin, Sean; Hope, H.

doi:10.1107/s0108768197015218

Cited by 40 publications

(59 citation statements)

References 10 publications

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“…H atoms were placed at calculated positions using suitable riding models with fixed isotropic thermal parameters [ U iso (H) = 1.2 U eqv (C) for CH groups and U iso (H) = 1.5 U eqv (C) for CH 3 ]. The relatively high R‐values for the vapor‐grown crystals, and especially of tBu‐BTBT , were largely a consequence of poor counting statistics caused by the extreme thinness of the crystals …”

Section: Methodsmentioning

confidence: 99%

Bulky End‐Capped [1]Benzothieno[3,2‐b]benzothiophenes: Reaching High‐Mobility Organic Semiconductors by Fine Tuning of the Crystalline Solid‐State Order

et al. 2015

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A series of bulky end-capped [1]benzothieno[3,2-b]benzothiophenes (BTBTs) are developed in order to tune the packing structure via terminal substitution. A coupled theoretical and experimental study allows us to identify 2,7-di-tert-butylBTBT as a new high-performance organic semiconductor with large and well-balanced transfer integrals, as evidenced by quantum-chemical calculations. Single-crystal field-effect transistors show a remarkable average saturation mobility of 7.1 cm(2) V(-1) s(-1) .

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Section: Methodsmentioning

confidence: 99%

Bulky End‐Capped [1]Benzothieno[3,2‐b]benzothiophenes: Reaching High‐Mobility Organic Semiconductors by Fine Tuning of the Crystalline Solid‐State Order

et al. 2015

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“…The authors describe the dehydration as reversible while it cannot be said whether the hydrate is stoichiometric or non-stoichiometric since the rehydration was carried out in a water saturated atmosphere-a condition in which both kinds of hydrates can be rehydrated. Some hydrates contain the water in discrete layers in the crystal structure, as shown by the example of uric acid dihydrate ( Figure 6) [46][47][48]. Although this feature is closely connected to higher guest mobility and thus could be assumed to be most common in non-stoichiometric hydrates, uric acid dihydrate in fact represents a stoichiometric hydrate which undergoes strong pseudomorphosis when dried.…”

Section: Single Crystal X-ray Structures Of Hydratesmentioning

confidence: 99%

X-ray and Neutron Diffraction in the Study of Organic Crystalline Hydrates

Fucke

Steed

2010

Water

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A review. Diffraction methods are a powerful tool to investigate the crystal structure of organic compounds in general and their hydrates in particular. The laboratory standard technique of single crystal X-ray diffraction gives information about the molecular conformation, packing and hydrogen bonding in the crystal structure, while powder X-ray diffraction on bulk material can trace hydration/dehydration processes and phase transitions under non-ambient conditions. Neutron diffraction is a valuable complementary technique to X-ray diffraction and gives highly accurate hydrogen atom positions due to the interaction of the radiation with the atomic nuclei.Although not yet often applied to organic hydrates, neutron single crystal and neutron powder diffraction give precise structural data on hydrogen bonding networks which will help explain why hydrates form in the first place.

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“…Afterward, the structures of UA [15] and UAD were determined with higher accuracy and precision [16]. Later, the similarity of uric acid and uric acid dihydrate structures was discussed, which led to the possibility of their epitaxial interaction [16,17]. Differences in the crystal structure associated with the presence of additional water molecules lead to a change in properties.…”

Section: Introductionmentioning

confidence: 99%

Thermal Behavior and Phase Transition of Uric Acid and Its Dihydrate Form, the Common Biominerals Uricite and Tinnunculite

et al. 2019

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Single crystals and powder samples of uric acid and uric acid dihydrate, known as uricite and tinnunculite biominerals, were extracted from renal stones and studied using single-crystal and powder X-ray diffraction (SC and PXRD) at various temperatures, as well as IR spectroscopy. The results of high-temperature PXRD experiments revealed that the structure of uricite is stable up to 380 °C, and then it loses crystallinity. The crystal structure of tinnunculite is relatively stable up to 40 °C, whereas above this temperature, rapid release of H2O molecules occurs followed by the direct transition to uricite phase without intermediate hydration states. SCXRD studies and IR spectroscopy data confirmed the similarity of uricite and tinnunculite crystal structures. SCXRD at low temperatures allowed us to determine the dynamics of the unit cells induced by temperature variations. The thermal behavior of uricite and tinnunculite is essentially anisotropic; the structures not only expand, but also contract with temperature increase. The maximal expansion occurs along the unit cell parameter of 7 Å (b in uricite and a in tinnunculite) as a result of the shifts of chains of H-bonded uric acid molecules and relaxation of the π-stacking forces, the weakest intermolecular interactions in these structures. The strongest contraction in the structure of uricite occurs perpendicular to the (101) plane, which is due to the orthogonalization of the monoclinic angle. The structure of tinnunculite also contracts along the [010] direction, which is mostly due to the stretching mechanism of the uric acid chains. These phase transitions that occur within the range of physiological temperatures emphasize the particular importance of the structural studies within the urate system, due to their importance in terms of human health. The removal of supersaturation in uric acid in urine at the initial stages of stone formation can occur due to the formation of metastable uric acid dihydrate in accordance with the Ostwald rule, which would serve as a nucleus for the subsequent growth of the stone at further formation stages; afterward, it irreversibly dehydrates into anhydrous uric acid.

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Uric Acid Dihydrate Revisited

Abstract: At 120 K, crystals of pure laboratory-grown uric acid dihydrate [7,9-dihydro-1H-purine-2,6,8(3H)

Cited by 40 publications

References 10 publications

Bulky End‐Capped [1]Benzothieno[3,2‐b]benzothiophenes: Reaching High‐Mobility Organic Semiconductors by Fine Tuning of the Crystalline Solid‐State Order

Bulky End‐Capped [1]Benzothieno[3,2‐b]benzothiophenes: Reaching High‐Mobility Organic Semiconductors by Fine Tuning of the Crystalline Solid‐State Order

X-ray and Neutron Diffraction in the Study of Organic Crystalline Hydrates

Thermal Behavior and Phase Transition of Uric Acid and Its Dihydrate Form, the Common Biominerals Uricite and Tinnunculite

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