Molecular Cocrystals of Carboxylic Acids. XXV The Utility of Urea in Structure Making with Carboxylic Acids and the Crystal Structures of a Set of Six Adducts with Aromatic Acids

Abstract

Molecular adducts of urea with six aromatic carboxylic acids have been prepared and characterized by using X-ray diffraction methods and infrared spectroscopy. These compounds are with 5-nitrosalicylic acid [(C₇H₅NO₅)₂(CH₄N₂O)] (1), 3,5-dinitrosalicylic acid [(C₇H₄N₂O₇)(CH₄N₂O)] (2), 4-aminobenzoic acid [(C₇H₇NO₂)₂(CH₄N₂O)] (3), o-phthalic acid [(C₈H₆O₄)(CH₄N₂O)] (4), pyrazine-2,3-dicarboxylic acid [(C₄H₄N₂O₄)(CH₄N₂O)] (5) and pyridine-2,6-dicarboxylic acid [(C₇H₅NO₄)(CH₄N₂O)₂] (6). In the majority of the adducts, all six potential interactive sites on the urea molecules are utilized in hydrogen bonding, giving polymeric structures.