Two benzamide-based derivatives were synthesized and their structures solved for the first time. The successful syntheses of N-ethyl-4-iodobenzamide (C9H10INO, NE4IBA) and N-ethyl-4-ethynylbenzamide (C11H11NO, NE4EBA) were achieved via a simple synthetic route. The molecules of NE4IBA in the crystal form one-dimensional double chains with strong hydrogen bonding and weak I⋯I halogen interactions, while NE4EBA forms two-dimensional hydrogen-bonded layers, including acetylene moieties engaging in C - H⋯O interactions within a rigid planar layer packing arrangement. Intermolecular N - H⋯O interactions between the amide groups dominate in both crystal structures. The strong exothermal effect of acetylene-group polymerization was detected immediately after melting NE4EBA using a simultaneous thermal analysis. © 2025 Rajakumar et al.
