The title compound, C(18)H(20)N(2)O(3), crystallizes as the keto tautomer, unlike the vast majority of similar structures that have been reported that contain the hydr-oxy tautomer. There are two strong hydrogen bonds in the crystal structure, both accepted by the same carbonyl group: one intra-molecular N-H⋯O and one inter-molecular O-H⋯O. As a result, the carbonyl C=O distance is long, at 1.3...

In the title compound, C(8)H(8)N(4)·C(8)H(8)N(4), two tautomers, viz. 3-phenyl-1,2,4-triazol-5-amine and 5-phenyl-1,2,4-triazol-3-amine, are crystallized together in equal amounts. The 3-phenyl-1,2,4-triazol-5-amine mol-ecule is essentially planar; the phenyl ring makes a dihedral angle of 2.3 (2)° with the mean plane of the 1,2,4-triazole ring. In the 5-phenyl-1,2,4-triazol-3-amine tautomer, t...

Quantum-chemical calculations were performed for all possible isomers of neutral aniline and its redox forms, and intramolecular proton-transfer (prototropy) accompanied by π-electron delocalization was analyzed. One-electron oxidation (PhNH(2) - e → [PhNH(2)](+•)) has no important effect on tautomeric preferences. The enamine tautomer is preferred for oxidized aniline similarly as for the neut...

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density functional theory (dft) based calculations have been performed to examine the relaxations of tautomers of 4–hydroxy–6–methylpyridin–2(1h)–one (mpo), as a representative of pyridinone derivatives, at the fullerene (c60) surfaces. optimized molecular properties including energies, dipole moments and atomic scale quadrupole coupling constants (cq) have been evaluated to investigate the str...

In the title mol-ecule, C(17)H(12)INO, the dihedral angle between the naphthaldeyde plane and the 3-iodo-aniline plane is20.07 (13)°. It exists in the solid state as an enol-imine tautomer with a strong intra-molecular O-H⋯N hydrogen bond.

The gas-phase acidity and proton affinity of thymine, cytosine, and 1-methyl cytosine have been examined using both theoretical (B3LYP/6-31+G*) and experimental (bracketing, Cooks kinetic) methods. This paper represents a comprehensive examination of multiple acidic sites of thymine and cytosine and of the acidity and proton affinity of thymine, cytosine, and 1-methyl cytosine. Thymine exists a...

In the ground electronic state, the first two (1 and 2) of the compounds investigated--9-(methoxyamino)acridine (1), 9-hydrazinoacridine (2), N-(2-chloroethyl)acridin-9-amine (3) and N-(5-methylpyridin-2-yl)acridin-9-amine (4)--exist principally in the imino tautomeric form, while the other two (3 and 4) can coexist as amino and imino tautomers in solvents of various polarities and abilities to...