2-(2-Oxazolin-2-yl)benzene-1,4-diol: X-ray and density functional theory studies

In the crystal structure of the title compound, C₉H₉NO₃, there are strong intra­molecular O—H...N and inter­molecular O—H...O hydrogen bonds which, together with weak inter­molecular C—H...O hydrogen bonds, lead to the formation of infinite chains of mol­ecules. The calculated inter­molecular hydrogen-bond energies are −11.3 and −2.7 kJ mol⁻¹, respectively, showing the dominant role of the O—H...O hydrogen bonding. A natural bond orbital analysis revealed the electron contribution of the lone pairs of the oxazoline N and O atoms, and of the two hydr­oxy O atoms, to the order of the relevant bonds.

3-(4-Bromo­phen­yl)-5-(4-dimethyl­amino­phen­yl)-1-phenyl-2-pyrazoline: X-ray and density functional theory (DFT) studies

In the crystal structure of the title compound, C₂₃H₂₂BrN₃, a strong conjugation of the pyrazoline chromophore with the aromatic rings at positions 1 and 3 is observed, as well as a significant shift in the synclinal→synperiplanar direction. The absolute structure was unequivocally determined. In the absence of clasical hydrogen-bond donors, the structure is stabilized by weak C—H...π inter­actions. This paper also reports the electronic structure of the title compound using NBO (natural bond order) analysis. The contributions of lone pairs to the relevant bonds were revealed.

(E)-Methyl 2-anilinomethyl­ene-3-oxo­butanoate: X-ray and density functional theory studies

Mol­ecules of the title compound, C₁₂H₁₃NO₃, are not planar and are stabilized by electrostatic inter­actions, as the dipole moment of the mol­ecule is 3.76 D. They are also stabilized by intra­molecular hydrogen bonds of N...O and C...O types, and by a complicated network of weak inter­molecular hydrogen bonds of the C...O type. This paper also reports the theoretical investigation of the hydrogen bonding and electronic structure of the title compound using natural bond orbital (NBO) analysis.