Uric Acid Dihydrate Revisited

Sean Parkin, Håkon Hope

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


At 120 K, crystals of pure laboratory-grown uric acid dihydrate [7,9-dihydro-1H-purine-2,6,8(3H)-trione dihydrate], C5H4N4O3.2H2O, are monoclinic, P21/c, with a = 7.237 (3), b = 6.363 (4), c = 17.449 (11) Å, β = 90.51 (1)°, Z = 4, wR2 (all data) = 0.1094, R1 = 0.0406 for data with I > 2σ(I). The crystals exhibit pseudo-orthorhombic twinning with refined twin fractions of 0.89 and 0.11. Within each twin, disorder about a noncrystallographic twofold exists with refined occupancies of 0.83 and 0.17. Packing consists of layers of hydrogen-bonded uric acid separated by layers of hydrogen-bonded water. The epitaxy of uric acid dihydrate with its anhydrous counterpart is readily explicable from the refined model. Treatment of the structure as twinned and disordered in space group P21/c fully accounts for well documented violations of systematic absences in orthorhombic space groups.

Original languageEnglish
Pages (from-to)339-344
Number of pages6
JournalActa Crystallographica Section B: Structural Science
Issue number3
StatePublished - Jun 1 1998

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology


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