The utility of 4-aminobenzoic acid in promotion of hydrogen bonding in crystallization processes: the structures of the cocrystals with halo and nitro subsituted aromatic compounds, and the crystal structures of the adducts with 4-nitroaniline (1:1), 4-(4-nitrobenzyl)pyridine (1:2), and (4-nitrophenyl)acetic acid (1:1)

A number of molecular adducts of 4-aminobenzoic acid (4-ABA) have been prepared and characterized using infrared spectroscopy and in three cases by X-ray diffration methods. These three compounds are with 4-nitroaniline (4-ABA) (C₆H₆N₂O₂)], 4-(4-nitrobenzyl) pyridine, (4-ABA)₂(C₁₂H₁₀N₂O₂)₄], and (4-nitrophenyl)acetic acid, (4-ABA) (C₈H₇NO₄)]. Other compounds described are with 4-chlorobenzoic acid, (4-ABA) (C₇H₅ClO₂)], 4-bromobenzoic acid, (4-ABA) (C₇H₅BrO₂)], 4-cyanobenzoic acid, (4-ABA) (C₇H₆N₂)], 2-nitrobenzoic acid, (4-ABA) (C₇H₅NO₄)], and 3-nitrobenzoic acid, (4-ABA) (C₇H₅NO₄)]. All compounds have 1:1 stoichiometry except that with 4-(4-nitrobenzyl)pyridine (1:2) which is unique in being retro-stoichiometric. A review of the systematics of the 4-aminobenzoic acid adducts is also made, particularly with respect to the infrared characterization of the cocrystalline materials and prediction of their NLO potential.