Ab initio and density functional theory (DFT) calculations on some model systems are presented to assess the extent to which intermolecular hydrogen bonding can affect the planarity of amide groups. Formamide and urea are examined as archetypes of planar and non-planar amides, respectively. DFT optimisations suggest that appropriately disposed hydrogen-bond donor or acceptor molecules can induc...

Each of the two independent mol-ecules of the title comound, C(14)H(20)N(2)O(3), exists in the zwitterionic form as the imino N atoms are protonated. The =N-H unit forms an intra-molecular hydrogen bond to the negatively charged O atom, and also a weaker intermolecular N-H⋯O bond, the latter resulting in inversion dimers.

Hydrogen bonding interaction is one of the most important intermolecular interactions. This interaction has been known almost for a century, but it is popular only after the work of Pauling, who was the first to give a definition of the hydrogen bond. According to Pauling, ‘under certain conditions an atom of hydrogen is attracted by rather strong forces to two atoms, instead of only one, so th...

The asymmetric unit of the title compound, C(8)H(9)Cl(2)NO, contains two crystallographically independent mol-ecules which are connected via an N-H⋯O hydrogen bond . There is aromatic π-π stacking in the crystal, with a centroid-centroid distance between benzene rings of 3.48 (2)Å. The crystal packing is stabilized by intermolecular hydrogen bonds.

An unprecedented intermolecular aliphatic C-F···H-C interaction was observed in the X-ray crystal structure of a fluorinated triterpenoid. Despite the notion of fluorine being a poor acceptor, computational and IR studies revealed this interaction to be a weak to moderate hydrogen bond with a C-H stretch vibration frequency blue-shifted by 14 cm-1 and d(F-H) = 2.13 Å. In addition, the aliphatic...

The asymmetric unit of the title compound, C(12)H(13)NO(3), contains two independent mol-ecules. The conformation of the N-H bond and the C=O bond in the amide segment are anti to each other. The mol-ecular conformation of each mol-ecule is stabilized by an intra-molecular O-H⋯O hydrogen bond. In the crystal, mol-ecules are connected through intermolecular N-H⋯O hydrogen bonds. In addition, the...

The title compound, C(9)H(8)N(2)O(8), was obtained by the reaction of imidazole-4,5-dicarb-oxy-lic acid and 2-chloro-acetic acid. An intra-molecular O-H⋯O hydrogen bond occurs. The crystal packing is stabilized by intermolecular O-H⋯O and C-H⋯O hydrogen bonds, which link mol-ecules into a three-dimensional network.

First-principles calculations were performed to study the hydrogen bond in the camphorsulfonic (CSA) acid-doped polyaniline system. The density functional theory (DFT) method was used to calculate the ground-state geometric structure optimization. Meanwhile, the electronic excitation energies and corresponding oscillation strengths of the low-lying electronically excited states were investigate...

In the title compound, C(13)H(14)N(2), the dihedral angle between the aromatic rings is 48.1 (1)° and the bridging C-N-C bond angle is 127.24 (12)°. In the crystal, intermolecular N-H⋯N hydrogen bonding about a center of inversion generates a hydrogen-bonded dimer.

The title compound, C(25)H(44)N(4)O(5), exhibits a turn with the main chain reversing direction, held together by an intramolecular N-H.O hydrogen bond. In the urea fragment, a notable amide C-N bond between the carboxyl C and the tertiary N atom shows marked single-bond character [1.437 (2) A]. The dihedral angle of the beta-alanyl residue, centrally located in the turn, is gauche [69.2 (2) de...