Carbonyl–carbonyl interactions and amide π‐stacking as the directing motifs of the supramolecular assembly of ethyl N ‐(2‐acetylphenyl)oxalamate in a synperiplanar conformation

The title compound, C 12 H 13 NO 4 , is one of the few examples that exhibits a syn conformation between the amide and ester carbonyl groups of the oxalyl group. This conformation allows the engagement of the amide H atom in an intramolecular three‐centred hydrogen‐bonding S (6) S (5) motif. The compound is self‐assembled by C=O...C=O and amide–π interactions into stacked columns along the b ‐axis direction. The concurrence of both interactions seems to be responsible for stabilizing the observed syn conformation between the carbonyl groups. The second dimension, along the a ‐axis direction, is developed by soft C—H...O hydrogen bonding. Density functional theory (DFT) calculations at the B3LYP/6‐31G(d,p) level of theory were performed to support the experimental findings.