Comment

Hydrogen bonds often provide the strongest intermolec-ular forces between molecules in organic molecular crystals and hence often dictate the preferred packing arrangement. The general principles underlying hydro-gen-bond formation are reasonably well understood and the structures of hydrogen-bonded crystals can often be rationalized in terms of the preferred combinations of hydrogen-bond donors and acceptors (Etter, 1990; Etter, McDonald & Bernstein, 1990; Etter & Reutzel, 1991). In general, the strongest hydrogen-bond donors pair off with the strongest hydrogen-bond acceptors. Similar pair-ing processes are repeated until all the hydrogen-bond donors and acceptors have been utilized. Herein we report the formation of a two-dimensional network of intermolecular N--H...O--C hydrogen bonds in the structure of 6-amino- 1,3-dimethyluracil (I)