MOLECULAR COCRYSTALS OF CARBOXYLIC-ACIDS .5. THE CRYSTAL-STRUCTURES OF (2-CARBOXY-PHENOXY)ACETIC ACID AND ITS 1-1 ADDUCT WITH 4-AMINOBENZOIC ACID

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 [0 ... 0, 2.67(l) angstrom]. The adduct (2) represents the first example of a phenoxyalkanoic involved in a hetero-dimer association through the conventional cyclic hydrogen-bonding system [0 ... 0, 2.54, 2.68(l) angstrom]. The 2-carboxy group is also weakly hydrogen bonded to the 4-amino group of (4-aba) [0 ... N, 2.99(1)angstrom], and in both (1) and (2) it has an intramolecular hydrogen bond to the ether oxygen of the oxyacetic acid side chain.