The title compound, C(10)H(14)N(4)O(2)S, exists in the amine tautomeric form. The dihedral angle between the benzene and thia-diazo-lidine rings is 66.54 (19)°. In the crystal, mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds into a layer parallel to the ac plane. The layers are further linked by C-H⋯O hydrogen bonds.

The mol-ecule of the title compound, C(14)H(10)N(2)O(2), adopts the phenol-imine tautomeric form. The dihedral angle between the planes of the two benzene rings is 13.84 (13)°. A strong intra-molecular O-H⋯N hydrogen-bonding inter-action stabilizes the mol-ecular conformation. In the crystal structure, centrosymmetrically related mol-ecules are linked into dimers by inter-molecular C-H⋯O and O-...

The title compound, C(17)H(19)NO(3), adopts the phenol-imine tautomeric form, with a resonance-assisted O-H⋯N intra-molecular hydrogen bond [O⋯N = 2.551 (3) Å]. The dihedral angle between the two benzene rings is 45.42 (7)°. The two meth-oxy groups are coplanar with the attached benzene ring [C-O-C-C torsion angles = -1.1 (5) and 3.2 (4)°].

Antibacteriophage antibiotics, RK-1441A and B, related to neothramycin were isolated from the culture broth of Streptomyces sp. and their structures were deduced from spectroscopic analyses. The structure of RK-1441A was 8,11-dihydroxy-3,7-dimethoxy-5-oxo-1H-pyrrolo[2,1-c:1,4]benzodiazepine. RK-1441B is a tautomeric mixture at C-3 of the structure, 3,8,11-trihydroxy-7-methoxy-5-oxo-1H-pyrrolo[2...

New Schiff bases have been prepared by reacting 3-hydroxy-4-pyridine- carboxaldehyde with various amines. NMR spectroscopic methods provided clear evidence that the Schiff bases exist in the solid state and in solution as hydroxyimino tautomers with the E-configuration. A study of the stabilities of the tautomeric forms and the different conformers has been carried out using density functional ...

This review intends to survey theoretical calculations for conformational and/or tautomeric equilibria of small organic molecules in solution. The phase “solution” should be emphasized, since many theoretical studies have considered gas-phase processes, whereas much less investigations have been performed for exploring equilibria in solution. Experimental studies available on this field are of ...

We have used the CNDO/2-CI method to calculate the isopotential maps for the fundamental state and the direction of the polarizations corresponding to several singlet transitions in the mole­ cules of guanine, cytosine and tautomeric forms. We have also calculated the times for proton tunneling and equilibrium constants between both conformers corresponding to the fundamental and some excited s...