Redetermination of orotic acid monohydrate

Abstract

The crystal structure of the title compound, which is also known as vitamin B13 (systematic name: 2,6-dioxo-1,2,3,6-tetra-hydro-pyrimidine-4-carboxylic acid monohydrate), C5H4N2O4·H2O, was reported for the first time by Takusagawa & Shimada [Bull. Chem. Soc. Jpn (1973), 46, 2011-2019]. The present redetermination provides more precise values of the mol-ecular geometry. The asymmetric unit comprises a planar diketo tautomer and a solvent water mol-ecule. In the crystal structure, mol-ecules are connected by O - H⋯O, N - H⋯O and C - H⋯O hydrogen bonds involving NH groups, two carbonyl O atoms and the solvent water mol-ecule.