A Serendipitous Synthesis of N,N'-Diethyloxamide: Crystallographic and Computational Analysis of its Solid-State Structure

A combined crystallographic/computational analysis focused on the supramolecular features of the crystal structure of N,N'-diethyloxamide (NNDO) is discussed in this work. The studied compound was obtained unexpectedly during the synthesis of a series of salts of cyclic oximes derivatives. In the solid state NNDO is stabilized essentially through a strong N–H···O hydrogen bond but Hirshfeld surface analysis and Density Functional Theory (DFT) calculations were carried out to evaluate the strength of the predominant hydrogen bonds observed in the X-ray structure, as well as the secondary CH···O and CH···N contacts established between the ethyl groups and the perpendicular dioxamide group. These interactions were further investigated using a combination of Quantum Theory of Atoms in Molecules (QTAIM) and Non-Covalent Interaction Plot (NCIplot) computational tools, and were rationalized using Molecular Electrostatic Potential (MEP) surface calculations.