Hydrogen bonding due to regioisomerism and its effect on the supramolecular architecture of diethyl 2-[(2/4-hydroxyanilino)methylidene]malonates.

Diethyl 2-[(2-hydroxyanilino)methylidene]malonate, (I), and diethyl 2-[(4-hydroxyanilino)methylidene]malonate, (II), both C(14)H(17)NO(5), crystallize in centrosymmetric orthorhombic and monoclinic crystal systems, respectively. Compound (I) resides on a crystallographic mirror plane and displays bifurcated intramolecular hydrogen bonding, as well as intermolecular hydrogen bonding due to the position of the hydroxy group. Compound (II) has a single intramolecular N-H...O hydrogen bond. Infinite one-dimensional head-to-tail chains formed by O-H...O hydrogen bonding are present in both structures. The molecular packing is mainly influenced by the intermolecular O-H...O interactions. Additionally, C-H...O interactions crosslinking the chains are found in (II).