The nature of the intramolecular hydrogen bond in the enol tautomer of 2,4-pentanedione has been investigated by high resolution proton and deuteron magnetic resonance spectroscopy. An unusually large deuterium isotope effect on the chemical shift of the bridge hydrogen has been observed. This unexpected result, together with the observation of a pronounced temperature dependence for both the p...

The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between "static" and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. ...

An NMR titration method has been used to simultaneously measure the acid dissociation constant (pKa) and the intramolecular NHO prototropic constant ΔKNHO on a set of Schiff bases. The model compounds were synthesized from benzylamine and substituted ortho-hydroxyaldehydes, appropriately substituted with electron-donating and electron-withdrawing groups to modulate the acidity of the intramolec...

The title compound, C(17)H(18)N(2)O(3), is approximately planar, owing in part to an intra-molecular bifurcated O-H⋯(N,O) hydrogen bond; the dihedral angle between the two aromatic rings is 23.86 (9)°. In the crystal struture, centrosymmetrically related mol-ecules associate into dimers via the eight-membered carboxyl-ate {⋯H-O-C=O}(2) synthon.

The title compound, C(16)H(16)BrNO(3), adopts an E configuration with respect to the imine C=N bond. The two benzene rings are twisted with respect to each other at an angle of 38.3 (1)°. In the crystal structure, mol-ecules are connected by weak bifurcated C-H⋯(O, O) hydrogen bonds, forming a helical chain along the b axis.

The solvothermal synthesis and crystal structure of [bis(thiocyanato-?N)bis(tris(pyridin-2-yl-?N)amine)iron(II)] ( 1 ) are described. obtained was i subjected to theoretical analysis interaction energies intra- intermolecular bonding. This comprehensive study illustrates the richness non-covalent interactions that exhibited by nitrile anionmetal complexes. neutral complex lies on a crystallogra...

The asymmetric unit of the title organic salt [systematic name: 1H-pyrazol-2-ium 2,4,6-tri-nitro-phenolate-1H-pyrazole (1/1)], H(C3H4N2)2 (+)·C6H2N3O7 (-), consists of one picrate anion and one hydrogen-bonded dimer of a pyrazolium monocation. The H atom involved in the dimer N-H⋯N hydrogen bond is disordered over both symmetry-unique pyrazole mol-ecules with occupancies of 0.52 (5) and 0.48 (5...

N-(o-methoxybenzamido)thioureas (2 X/2 Y) are found to show an enhanced anion binding affinity with binding constants over 10(7) mol(-1) L orders of magnitude for AcO(-) and a redshifted absorption of the anion binding complexes in acetonitrile (MeCN) relative to those of N-benzamidothioureas (1) that bear no o-OMe in the N-benzamide moiety, despite the electron-donating character of o-OMe. Abs...

In the title mol-ecule, C(12)H(11)N(3)O(2), the dihedral angle between the mean planes of the naphthalene and carboxamide groups is 28.9 (8)°. The hydrazine N atoms are twisted slightly out of the plane of the carboxamide group [C-C-N-N torsion angle = -175.06 (13)°]. The crystal packing is influenced by N-H⋯O hydrogen bonding which includes a bifurcated hydrogen bond between the amide N atom a...

Arzanol is a naturally-occurring prenylated acylphloroglucinol isolated from Helichrysum italicum and exhibiting anti-oxidant, antibiotic and antiviral activities. The molecule contains an α-pyrone moiety attached to the phloroglucinol moiety through a methylene bridge. The presence of several hydrogen bond donor or acceptor sites makes intramolecular hydrogen bonding patterns the dominant stab...