[reaction: see text] We report for the first time that stoichiometric and even catalytic quantities of weak acids in aqueous solution can very efficiently catalyze amide isomerization in a carefully designed system in which a proton donor is situated so that intramolecular hydrogen bonding to the amide nitrogen is highly favored. Our results provide the first experimental verification that hydr...

In the crystal structure of the title compound, C(13)H(8)O(4), the inversely oriented mol-ecules form inversion dimers through pairs of O-H⋯O hydrogen-bonding inter-actions. An intramolecular O-H⋯O hydrogen bond occurs. In the packing of the mol-ecules, the nearly planar 2-(furan-2-yl)-4H-chromene units [dihedral angle between the chromene and furan rings = 3.8 (1)°] are either parallel or incl...

Proton transfer and hydrogen bonding are two aspects of the chemistry of hydrogen that respectively govern the behaviour and structure of many molecules, both simple and complex. All the theoretical enol and keto conformations of 1,3-diphenyl-1,3propandion known as dibenzoylmethane (DBM), have been investigated by means of atoms in molecules (AIM) theory. It was found that the most stable confo...

In the title compound, C(11)H(16)N(4)O(2), the dihedral angle between the benzene ring and the plane of the four carbon atoms in the piperazine ring is 12.17 (3)°; the latter ring adopts a chair conformation. An intramolecular N-H⋯O hydrogen bond generates an S(6) ring. In the crystal, the molecules are linked by N-H⋯N hydrogen bonds, forming chains.

In the zwitterionic mol-ecule of the title compound, C(10)H(7)N(3)O(4)·H(2)O, one carboxyl group is deprotonated and the pyridine N atom is protonated. The pyridinium and imidazole rings form a dihedral angle of 5.23 (1)°. An intramolecular O-H⋯O hydrogen bond occurs. In the crystal, inter-molecular N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds link the zwitterions and water mol-ecules into sheets para...

Explicit-solvent molecular dynamics simulations (50 ns, 300 K) of the eight reducing glucose disaccharides (kojibiose, sophorose, nigerose, laminarabiose, maltose, cellobiose, isomaltose, and gentiobiose) have been carried out using the GROMOS 45A4 force field (including a recently reoptimized carbohydrate parameter set), to investigate and compare their conformational preferences, intramolecul...

The title compound, C(28)H(22)O(6)S(2)·2C(6)H(13)N·2H(2)O, was prepared by the reaction of a Wittig reagent and 2-formyl-benzene-sulfonic acid. The main molecule lies about an inversion centre at the midpoint of the C-C bond between the inner benzene rings. The mol-ecular conformation is stabilized by intramolecular hydrogen bonds. The crystal structure is further stabilized by O-H⋯O and N-H⋯O ...

The title Schiff base compound, C(14)H(9)Br(2)ClN(2)O(2)·CH(4)O, was derived from the condensation reaction of 3,5-dibromo-salicylaldehyde with 2-chloro-benzohydrazide. The dihedral angle between the two benzene rings is 48.2 (2)°. In the crystal structure, mol-ecules are linked through O-H⋯O and N-H⋯O inter-molecular hydrogen bonds, forming layers parallel to the bc plane. There is also an O-H...

The molecule of the dinuclear title compound, [Tl(2)(C(9)H(10)NS(2))(6)], possesses a crystallographically imposed centre of symmetry. Each Tl(III) atom is seven-coordinated by S atoms of four different dithio-carbamate anions in a distorted penta-gonal-bipyramidal coordination geometry. The crystal structure is stabilized by a C-H⋯S hydrogen-bond inter-action linking complex mol-ecules into ch...

Convergent preparative routes to new urea-pyrazolate dinucleating ligands are described. Metal complexes of these ligands have hydrogen bond donors that are proximal to the metal centers that interact with other coordinated species. This is exemplified by Co(II) dimers with Co(II)-mu-Cl-Co(II) motifs, in which the chloro ligand is involved in four intramolecular hydrogen bonds. These noncovalen...