Crystal structure of 1:1 complex of barbital with 1-methylimidazole.

The prediction of a strong hydrogen-bonding interaction between barbital and 1-methylimidazole was confirmed. Two crystal complexes were obtained, 1:1 and 2:1, and the X-ray structure was determined for the 1:1 complex, which is monoclinic, space group P21/c, with a = 12.236(3) A, b = 11.332(4) A, c = 12.495(4) A, and beta = 120.67(1) degrees. The structure contains disk-shaped hydrogen-bonded tetramers with two molecules of each kind. There is a short NH...N hydrogen bond (2.82 A) in which barbiturate provides the NH donor.