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

In this study, we present the synthesis and structure characterization by single -crystal X-ray Diffraction (SCXRD), 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-cyanoN -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 (S N 2) 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 P 2 1 / c and P 2 1 / n , respectively. The Hirshfeld Surface Analysis revealed that the main contributions in the crystal packing have H center dot center dot center dot H, H center dot center dot center dot N/N center dot center dot center dot H, H center dot center dot center dot C/C center dot center dot center dot H and H center dot center dot center dot O/O center dot center dot center dot 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.