In the present work, DFT calculations are employed to obtain the optimized structures of 4- acyl pyrazolone tautomers (19 tautomers) using B3LYP/6-311++G** calculations. In addition, molecular parameters, IR frequencies and relative energies are extracted for all tautomers. The existence of aromatic ring, keto tautomer (versus enol tautomer), N-H bond (versus C-H bond) and C=N double bond (vers...

The mol-ecule of the title compound, C(11)H(11)N(3)O(5), exists as the E isomer as it is stabilized by an intra-molecular hydrogen bond. Except for the methyl H atoms, all atoms lie in special positions on a mirror plane and form a large conjugated system; the methyl H atoms are disordered about the mirror plane. In the crystalline state, bifurcated intra- and inter-molecular N-H⋯O hydrogen bon...

In the title solvate, C15H15N3O2S·CH3OH, the thio-semicarbazone mol-ecule is approximately planar; the maximum deviation from the mean plane is 0.4659 (14) Å and the dihedral angle between the aromatic rings is 9.83 (8)°. This conformation is supported by an intra-molecular N-H⋯N hydrogen bond. In the crystal, the thio-semicarbazone mol-ecules are linked into dimers by pairs of N-H⋯S hydrogen b...

The title compound, C 6 H 8 N 2 O 4 , a new derivative of isoxazole, has been synthesized and structurally characterized. crystal structure shows the molecule to be almost planar (r.m.s. deviation for non-hydrogen atoms = 0.029 Å), this conformation being supported by an intramolecular N—H...O hydrogen bond. In extended structure, molecules are linked bonds into chains propagating along [010].

The nature of resonance-assisted hydrogen bonds (RAHB) is still subject of an ongoing debate. We therefore analyzed the σ and π charge redistributions associated with the formation of intramolecular hydrogen bonds in malonaldehyde (MA) and its saturated analogue 3-hydroxypropanal (3-OH) and addressed the question whether there is a resonance assistance phenomenon in the sense of a synergistic i...

The title compound, C18H20N2O3S, exists as the phenol-imine form in the crystal and there are bifurcated intra-molecular O-H⋯(N/O) hydrogen bonds present. The conformation about the C=N bond is anti (1E); the C=N imine bond length is 1.287 (4) Å and the C=N-C angle is 122.5 (3)°. In the tetrahydrothienopyridine moiety, the six-membered ring has a flattened-boat conformation. In the crystal, mol...

In the title compound, C(16)H(9)F(4)N(3)O(2), the dihedral angle between the aromatic ring systems is 4.10 (14)° and a bifurcated intra-molecular N-H⋯(O,F) hydrogen bond generates an S(6) ring for the O-atom acceptor and an S(5) ring for the F-atom acceptor. A short C-H⋯O conact also occurs. In the crystal, mol-ecules are linked by C-H⋯O inter-actions.

The acidity constants of 5-uracilmethylphosphonic acid, H2(5Umpa), and 6-uracilmethylphosphonic acid, H2(6Umpa), were determined by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 M, NaNO3). Comparison of these constants with those of related uracil derivatives (partly taken from the literature) allows the conclusion that an intramolecular hydrogen bond is formed between (N1)H ...

Hydrogen bond strength in host-guest systems is modulated by many factors including preorganization, steric effects, and electronic effects. To investigate how electronic effects impact barbiturate binding in bifurcated Hamilton receptors, a library of receptors with differing electronic substituents was synthesized and (1)H NMR titrations were performed with diethyl barbital. The Hammett plot ...

In the crystal structure of the title salt, C9H22N2 (2+)·2NO3 (-), the piperidine ring of the dication adopts a chair conformation and the orientation of the C-NH3 bond is equatorial. The ions are linked by normal and bifurcated N-H⋯O hydrogen bonds in R 2 (2)(6), two R 4 (2)(8) and R 3 (4)(14) graf-set motifs, generating a three-dimensional network.