Three new pseudopolymorphs of 6-aminouracil.

Since 6-aminouracil derivatives show diversified use in various fields of application, we crystallized 6-aminouracil to examine its preferred hydrogen-bonding frameworks. 6-Aminouracil shows two rigid hydrogen-bonding sites, viz. one acceptor-donor-acceptor (ADA) site and one donor-donor-acceptor (DDA) site. During various crystallization attempts, we obtained three structures, namely two dimethylacetamide monosolvates, C4H5N3O2·C4H9NO, and a 1-methylpyrrolidin-2-one monosolvate, C4H5N3O2·C5H9NO. In all three structures, R2(1)(6) N-H...O hydrogen-bonding patterns link the molecules to their respective solvent molecules. The formation of R2(2)(8) N-H...O hydrogen-bond motifs between 6-aminouracil molecules can only be found in two-dimensional frameworks, whereas R3(3)(14) N-H...O patterns are present when zigzag chzins of 6-aminouracil molecules are formed.