Abstract
2,4-dihydr-oxy-5-iodo-pyrimidine), C(4)H(3)IN(2)O(2), which was first reported by Sternglanz, Freeman & Bugg [Acta Cryst. (1975 ▶), B31, 1393-1395], has been redetermined, providing a significant increase in the precision of the derived geometric parameters. The asymmetric unit comprises a non-planar mol-ecule in a slightly distorted B(25) boat conformation. The mol-ecules are associated in the crystal structure to form ribbons stabilized by N-H⋯O hydrogen bonds which involve NH groups and two carbonyl O atoms.