The characteristics of the intramolecular hydrogen bonding for a series of 19 different derivatives of 𝛽-aminoacroleine have been systematically analysed at the B3LYP/6-31G^∗∗ level of theory. The topological properties of the electron density distributions for N-H$\cdots$O intramolecular bridges have been analysed by the Bader theory of atoms in molecules. The electron density (𝜌) and Laplacian ($\nabla^2 \rho$) properties at critical points of the relevant bonds, estimated by AIM calculations, showed that N-H$\cdots$O have low and positive character ($\nabla^2 \rho > 0$), consistent with electrostatic character of the hydrogen bond. The vibrational study of the hydrogen bonded systems showed negative (red) shifts for the $\nu_{(N−H)}$ stretching mode. The 𝜋-electron delocalization parameter (𝑄) as a geometrical indicator of a local aromaticity and the geometry-based HOMA have also been calculated. Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by natural bond orbital (NBO) methods support the DFT results. The results of AIM and NBO analysis as well as $\nu_{(N−H)}$ were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. The various correlations were found between geometrical, energetic and topological parameters. The substituent effect was also analysed and it was found that the strongest hydrogen bonds exist for N⁺(CH₃)₃ and Cl substituents while the weakest ones for COOCH₃.

In the present work, a conformational analysis of 3-Hydroxy-propeneselenal is performed using several computational methods, including HF, DFT (B3LYP), and G2MP2 levels of theory. The relative electronic energies, the molecular structure, and intramolecular hydrogen bond energies are reported. Twenty different conformers were obtained, the most stable ones being planar. The conformational preference of this molecule was found to be mainly determined by the formation of Se…H-O and Se-H…O intramolecular hydrogen bonds, which are assisted by 𝜋-electron resonance. The atoms in molecules (AIM) theory of Bader, which is based on topological properties of the electron density, was used to analyze critical points and to study the nature of hydrogen bonds in these systems. NMR and natural bond orbital (NBO) analyses were also performed for a better understanding of the nature of intramolecular interactions in 3-Hydroxy-propeneselenal. Furthermore, calculations for all the possible conformations of the title compound in solution were also carried out at the B3LYP/6-311++G(d,p) level of theory (in three models such as polarizable continuum model (PCM), IEFPCM, and self−consistent isodensity polarized continuum model (SCIPCM).

The molecular structures and intramolecular hydrogen bond of Droxidopa have been investigated with density functional theory. It is found that strong hydrogen bonds (O–H…N and O…H–O) exist in the title compound. These hydrogen bonds play essential roles in determining conformational preferences and energy, which would have important effects in biological activity mechanisms that will strongly influence its characteristics in solution. A computational study of a representative number of actual and model structures was carried out in five solvents with different polarities and different types of interactions with solute molecules: water, ethanol, carbon tetrachloride, dimethyl sulfoxide, and tetrahydrofuran, utilizing the polarizable continuum model (PCM) model. The calculations were performed at the B3LYP/6-311++G(d,p) level of theory. In addition, the topological properties of the electron density distributions for O–H…N(O) intramolecular hydrogen bond were analyzed in terms of the Bader’s theory of atoms in molecules. Furthermore, the analyses of different hydrogen bonds in this molecule by quantum theory of natural bond orbital (NBO) methods support the density functional theory (DFT) results.

An environmentally friendly protocol is described for an economic, practical laboratory-scale oxidation of primary and secondary alcohols to aldehydes and ketones, using a bis-chloro-bridged binuclear Cu(II) complex [(HL)Cu(𝜇₂-Cl)₂Cu(HL)]*1.5 CH₃OH as catalyst. The catalyst was prepared in situ from commercially available reagents and is characterized by single crystal X-ray analysis, FT-IR, UV-visible spectra, mass spectrometry, and powder x-ray diffraction (PXRD). The geometry of the complex has been optimized using the B3LYP level of theory confirming the experimental data. Our results demonstrated well the efficiency, selectivity and stability of this new catalyst in the oxidation of alcohols in ethanol and tert-butyl hydroperoxide (tBuOOH) as a green solvent and oxidant, respectively. Turnover number and reusability have proven the high efficiency and relative stability of the catalyst.