Crystal structure, Hirshfeld surface analysis and DFT study of 1-ethyl-3-phenyl-1,2-di­hydro­quinoxalin-2-one

In the title mol­ecule, C(16)H(14)N(2)O, the di­hydro­quinoxaline moiety is not planar as there is a dihedral angle of 4.51 (5)° between the constituent rings. In the crystal, C—H⋯O hydrogen bonds form helical chains about the crystallographic 2(1) screw axis in the b-axis direction. Hirshfeld surface analysis indicates that the most important contributions to the crystal packing are from H⋯H (51.7%), H⋯C/C⋯H (26%) and H⋯O/O⋯H (8.5%) inter­actions. The optimized structure calculated using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level is compared with the experimentally determined structure in the solid state. The calculated HOMO–LUMO energy gap is 3.8918 eV.