β-Diketone interactions. Part 11. The hydrogen-bonded adduct 4, 6-dimethylpyrimidin-2-one·urea (DMP·U) from the reaction of pentane-2,4-dione and urea
Abstract
The X-ray crystal Structure of the adduct formed between 4,6-dimethylpyrimidin-2-one and urea (DMP·U) shoes a compact unit joined through two N–H ⋯ OC hydrogen bonds. One of these is remarkably short with RN ⋯ O 2.735 Å(RH ⋯ O 1.705 Å), and is believed to be among the shortest example of an NHO hydrogen bond between neutral molecules. Its hydrogen-bond energy, estimated from IR data, is ca. 75 kJ mol–1