Intramolecularly hydrogen-bonded

Marzocchi M P, Mantini A R, Casu M and Smulevich G 1997 Intramolecular hydrogen bonding and excited state proton transfer in hydroxyanthraquinones as studied by electronic spectra, resonance Raman scattering, and transform analysis J. Chem. Phys. 108 1-16... 

Construct molecular models of the gauche and anti conformations of 1 2 ethanediol and explore the possibility of intramolecular hydrogen bond formation in each one... 

Intramolecular hydrogen bonding is present in the chiral diastereomer of 225 5 tetra methylhexane 3 4 diol but absent in the meso diastereomer Construct molecular models of each and suggest a reason for the difference between the two... 

Intramolecular hydrogen bond between the —OH group and the carbonyl oxygen... 

Both enols have their carbon-carbon double bonds conjugated to a carbonyl group and can form an intramolecular hydrogen bond They are of comparable stability... 

Salicylate anion is a weaker base than p hydroxybenzoate because it is stabilized by intramolecular hydrogen bonding... 

Conjugation is more important 1 3 Cyclohexanedione exists mainly in its enol form in spite of the fact that intramolecular hydrogen bonding is impossible due to the distance between the carbonyl group and the enohc —OH group... 

Secondary structure refers to the shape of the molecule as a whole, particularly to those aspects of structure which are stabilized by intramolecular hydrogen bonds. 

The location of the hydroxyl and aldehyde groups ortho to one another in saUcylaldehyde permits intramolecular hydrogen bonding, and this results in the lower melting point and boiling point and the higher acid dissociation constant observed relative to -hydroxybenzaldehyde. 

Maleic and fiimaric acids have physical properties that differ due to the cis and trans configurations about the double bond. Aqueous dissociation constants and solubiUties of the two acids show variations attributable to geometric isomer effects. X-ray diffraction results for maleic acid (16) reveal an intramolecular hydrogen bond that accounts for both the ease of removal of the first carboxyl proton and the smaller dissociation constant for maleic acid compared to fumaric acid. Maleic acid isomerizes to fumaric acid with a derived heat of isomerization of —22.7 kJ/mol (—5.43 kcal/mol) (10). The activation energy for the conversion of maleic to fumaric acid is 66.1 kJ/mol (15.8 kcal/mol) (24). 

Fig. 3. Representations of sucrose in its crystalline conformation intramolecular hydrogen bonds are shown as dashed lines.

Conformation. Neutron diffraction studies of sucrose revealed the presence of two strong intramolecular hydrogen bonds 0-2—HO-1 and 0-5—HO-6 in the crystal form (7,8). These interactions hold the molecule in a weU-ordered and rigid conformation. The two rings are disposed at an angle close to 90°, with the glucopyranosyl and fmctofuranosyl residues adapting chair and T" twist conformations, respectively. 

Indanthrones. Indanthrone blue (Cl Vat Blue 4) [81-77-6] (6) (Cl 69800) is the first invented anthraquinone vat dye, and has been extensively used as the most important vat dye for many decades because of its bright color as well as excellent affinity and fastness. These advantages are considered to be due to the stable stmcture attained by the intramolecular hydrogen bonding (145). 

Acyl-, 4-alkoxycarbonyl- and 4-phenylazo-pyrazolin-5-ones present the possibility of a fourth tautomer with an exocyclic double bond and a chelated structure. The molecular structure of (138) has been determined by X-ray crystallography (Table 5). It was shown that the hydroxy group participates in an intramolecular hydrogen bond with the carbonyl oxygen atom of the ethoxycarbonyl group at position 4 (8OCSCII21). On the other hand, the fourth isomer is the most stable in 4-phenylazopyrazolones (139), a chelated phenyl-hydrazone structure. 

C NMR, 6, 398 molecular dimensions, 6, 397 tautomerism, 6, 404 Furoxan-3-carbohydra2ide intramolecular hydrogen bonding, 6, 396 Furoxan-3-carboxamide intramolecular hydrogen bonding, 6, 396 Furoxancarboxylic acids reactions, 6, 413 with nucleophiles, 6, 406 Furoxan-3,4-dicarbaldoxime synthesis, 6, 409 Furoxanoaaines fused... 

DFT STUDY OF 8-MERCAPTOQUINOLINE INTRAMOLECULAR HYDROGEN BOND, SINGLE PROTON TRANSFER AND WATER-ASSISTED TAUTOMERIZATION... 

Among numerous examples of the role of the chemical structure in tunneling rotation we select just one, connected with the effect of intramolecular hydrogen bond. In acetyl acetone in stable enol form... 

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