Hydrogen-Bonding in the Anhydrous Morpholinium Salts of the Three Isomeric Monoaminobenzoic Acids

摘要

The structures of the anhydrous morpholinium salts of the isomeric 2-aminobenzoic acid (anthranilic acid) (1), 3-aminobenzoic acid (2) and 4-aminobenzoic acid (3), with formula C4H10NO+ C7H8NO2 (-), have been determined. Crystals of 1 are monoclinic, space group P2(1) /c, with unit cell dimensions a = 11.0696(9), b = 7.8775(6), c = 13.0180(11) , beta = 95.804(8)A degrees and Z = 4. Compound 2 is orthorhombic, space group Pna2(1), with unit cell dimensions a = 9.3899(4), b = 16.6789(7), c = 7.4463(3) and Z = 4 and compound 3 is monoclinic, space group Cc, with unit cell dimensions a = 5.9233(6), b = 18.048(2), c = 10.5478(10) , beta = 90.376(10)A degrees and Z = 4. In all crystals, both morpholinium N-H atoms are involved in primary inter-species hydrogen-bonding interactions with carboxyl O-atom acceptors of the anions. Secondary N-H center dot center dot center dot O hydrogen bonds between the amine groups and carboxyl (1 and 3) or both carboxyl and morpholine O-atom acceptors in 2, including in 2 a three-centre asymmetric N-H center dot center dot center dot O,O' chelate [(4)] motif, give two-dimensional layers (1 and 2) or a three-dimensional network structure (3). In 1, the interactions include a centrosymmetric cyclic (12) motif and in 2, a cyclic (11) motif but no pi-pi aromatic ring associations are present in any of the structures.