Molecular Cocrystals of Carboxylic-Acids. V. The Crystal-Structures of (2-Carboxy-phenoxy)acetic Acid and Its 1 : 1 Adduct With 4-Aminobenzoic Acid

Abstract

The crystal structures of (2-carboxyphenoxy)acetic acid (cpaa) (1) and its 1 : 1 adduct [( cpaa )(4-aba)] (2) with 4-aminobenzoic acid have been determined by X-ray diffraction and refined to residuals R 0.077, (1), and 0.051, (2), for 783 and 1062 observed reflections, respectively. The dicarboxylic acid (1) is extended into a one-dimensional zig-zag polymer by hydrogen bonding through the two acid groups [O…O, 2.67(1)Ǻ]. The adduct (2) represents the first example of a phenoxyalkanoic involved in a hetero-dimer association through the conventional cyclic hydrogen-bonding system [O…O, 2.54, 2.68(1)Ǻ]. The 2-carboxy group is also weakly hydrogen bonded to the 4-amino group of (4-aba) [O…N, 2.99(1)Ǻ], and in both (1) and (2) it has an intramolecular hydrogen bond to the ether oxygen of the oxyacetic acid side chain.