Ethyl 2-[4-(4-meth-oxy-benz-yl)-3-methyl-6-oxopyridazin-1-yl]acetate.

In the title mol-ecule, C17H20N2O4, the inner part of the ester substituent is nearly perpendicular to the di-hydro-pyridazine ring, forming a dihedral angle of 83.21 (7)°. In the crystal, inversion dimers are formed by pairwise C-H⋯O inter-actions with the dimers connected into chains extending along the b-axis direction by C-H⋯π(ring) inter-actions. The chains are connected by π-stacking inter-actions to give corrugated layers parallel to the ab plane. The terminal ethyl group is disordered over two two sets of sites with the major component having a site occupancy factor of 0.715 (10).

Crystal structure and Hirshfeld surface analysis of (E)-3-benzyl-idene-4-oxo-penta-noic acid.

The asymmetric unit of the title mol-ecule, C12H12O3, contains two independent mol-ecules having opposite conformations and each forming self-dimers through complementary O-H⋯O hydrogen bonds. These dimers are linked by weak C-H⋯π inter-actions and C-H⋯O hydrogen bonds into a three-dimensional structure in which one can discern layers parallel to the bc plane. A Hirshfeld surface analysis of the inter-molecular inter-actions is included.

Ethyl 2-(4-benzyl-3-methyl-6-oxo-1,6-dihydropyridazin-1-yl)acetate: crystal structure and Hirshfeld surface analysis.

The title compound, C16H18N2O3, is constructed about a central oxopyridazinyl ring (r.m.s. deviation = 0.0047 Å), which is connected to an ethyl-acetate group at the N atom closest to the carbonyl group, and benzyl and methyl groups second furthest and furthest from the carbonyl group, respectively. An approximately orthogonal relationship exists between the oxopyridazinyl ring and the best plane through the ethyl-acetate group [dihedral angle = 77.48 (3)°]; the latter lies to one side of the central plane [the Nr-Nr-Cm-Cc (r = ring, m = methyl-ene, c = carbon-yl) torsion angle being 104.34 (9)°]. In the crystal, both H atoms of the N-bound methyl-ene group form methyl-ene-C-H⋯O(ring carbon-yl) or N(pyridazin-yl) inter-actions, resulting in the formation of a supra-molecular tape along the a-axis direction. The tapes are assembled into a three-dimensional architecture by methyl- and phenyl-C-H⋯O(ring carbon-yl) and phenyl-C-H⋯O(ester carbon-yl) inter-actions. The analysis of the calculated Hirshfeld surface indicates the dominance of H⋯H contacts to the overall surface (i.e. 52.2%). Reflecting other identified points of contact between mol-ecules noted above, O⋯H/H⋯O (23.3%), C⋯H/H⋯C (14.7%) and N⋯H/H⋯N (6.6%) contacts also make significant contributions to the surface.