Spectroscopic Characterization, Hirshfeld Surface, DFT, and TD-DFT of tert-Butyl Phenethylcarbamate and 1,1-Dimethyl-3-Phenethylurea

Abstract

Tert-butylphenethylcarbamate (1) and 1,1-dimethyl-3-phenethylurea (2) were synthesized, and their structures were confi rmed by NMR, FTIR, and mass spectrometry techniques. The experimental spectroscopic data of 1 and 2 were compared with the corresponding calculated ones obtained by density functional theory (DFT) and time-dependent DFT methods, for which the hybrid functionals B3LYP, B3P86, and PBE0 combined with the 6-311++G(d,p) basis set were tested. The solvent effect was considered using the implicit model — integral equation formalism-polarizable continuum model (IEFPCM). Relatively good correlation (R2 > 90%) was obtained between the experimental and predicted spectral data. The conformational effect on the absorption maximum λmax was negligible, that is, λmax of different conformers varied by less than 0.01 nm. Hirshfeld surface analysis and electrostatic potential calculations of the closest intermolecular contacts between active atoms of 1 and 2 revealed that the closest interactions were between hydrogen atoms of 39.6 and 46.3%, respectively.