The asymmetric units of the title compounds both contain one nonplanar molecule. In 4-benzyl-6-phenyl-4,5-dihydropyridazin-3(2H)-one, C17H14N2O, (I), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 46.69 (9)°; the phenyl ring of the benzyl group is nearly perpendicular to the plane of the pyridazine ring, the dihedral angle being 78.31 (10)°. In methyl 2-[5-(2,6-dichlorobenzyl)-6-oxo-3-phenyl-1,4,5,6-tetrahydropyridazin-1-yl]acetate, C20H16Cl2N2O3, (II), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 21.76 (18)°, whereas the phenyl ring of the dichlorobenzyl group is inclined to the pyridazine ring by 79.61 (19)°. In the crystal structure of (I), pairs of N—H...O hydrogen bonds link the molecules into inversion dimers with an R 2 2(8) ring motif. In the crystal structure of (II), C—H...O hydrogen bonds generate dimers with R 1 2(7), R 2 2(16) and R 2 2(18) ring motifs. The Hirshfeld surface analyses of compound (I) suggests that the most significant contributions to the crystal packing are by H...H (48.2%), C...H/H...C (29.9%) and O...H/H...O (8.9%) contacts. For compound (II), H...H (34.4%), C...H/H...C (21.3%) and O...H/H...O (16.5%) interactions are the most important contributions.
Chemistry and Pharmacology