Intermolecular interaction of azide, cyano and alkyne-N-phenethylacetamide dimers: Experimental and quantum chemical approach

Abstract

In this study, we present the synthesis and structure characterization by single-crystal X-ray Diffraction (SC-XRD), Ultraviolet Spectroscopy (UV), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR) and High-resolution Mass Spectrometry (HRMS) of 2-azido-N-phenethylacetamide (4) and 2-cyano-N-phenethylacetamide (6). Further, Density Functional Theory (DFT) was employed to get a better insight regarding the properties exhibited by the compounds. The computational chemistry has been used to explain and investigate the bimolecular nucleophilic substitution (SN2) and concerted acyl substitution mechanisms for the synthesis of compounds 4 and 6, respectively. Additionally, intrinsic reaction coordinate (IRC) calculations confirm the transition state for these reactions. The X-ray diffraction analysis showed that the compounds 4 and 6 crystallized as monoclinic systems, in space group P21/c and P21/n, respectively. The Hirshfeld Surface Analysis revealed that the main contributions in the crystal packing have H···H, H···N/N···H, H···C/C···H and H···O/O···H interactions. The frontier molecular orbital energies were calculated and the HOMO-LUMO energy gap of 4 and 6 were 10.011 and 10.278 eV, respectively. Theoretical values of electronic transitions, vibrational frequencies and NMR chemical shifts were calculated and compared with experimental results, they all showed good results.