Acid-base chemistry hydrogen bonding

Solvent extraction of metals embodies all aspects of coordination chemistry rates, equilibria, stereochemistry, crystal field theory, covalent bonding, hard-soft acid-base theory, hydrogen bonding, steric hindrance, enthalpy and entropy. All of these basic principles can link together to produce pure metals on an industrial scale from dilute aqueous solutions — a remarkable achievement of elegant coordination chemistry. To achieve this result it is only necessary to form within the aqueous medium a neutral species containing the metal to be extracted. 

Langlet, J., Claverie, P., Caron, R, Boeuve, J. C. (1981). Interactions between nucleic acid bases in hydrogen bonded and stacked configurations The role of the molecular charge distribution. International Journal of Quantum Chemistry, 20, 299. 

Electronic characteristics and their effects on the ability of side chains to engage in ionic bonding, covalent bonding, hydrogen bonding, van der Waals forces, and acid-base chemistry... 

The general or universal effects in intermolecular interactions are determined by the electronic polarizability of solvent (refraction index n0) and the molecular polarity (which results from the reorientation of solvent dipoles in solution) described by dielectric constant z. These parameters describe collective effects in solvate s shell. In contrast, specific interactions are produced by one or few neighboring molecules, and are determined by the specific chemical properties of both the solute and the solvent. Specific effects can be due to hydrogen bonding, preferential solvation, acid-base chemistry, or charge transfer interactions. 

Various mono- and bistriazines have been synthesized by Moral et al. [23] under microwave conditions. The use of a diamine bearing amino groups of different reactivities, selectively gave monotriazines (vii), bistriazines with identical substituents (viii) and differently substituted bistriazines (ix). The newly synthesized bistriazines showed promising applications in supramolecular chemistry based on hydrogen bonds and/or complexation with metals. They are also expected to show interesting fluorescence properties by complexation with cyan-uric and barbituric acid derivatives. 

The range of functionality provided by the 20 amino acids found in proteins consists of weak acids and bases, nucleophiles, hydrogen bond donors and acceptors, and the redox active thiol/disulfide. This limited range of chemistry is inadequate for the catalysis of many reactions found to occur in biological systems. Therefore, a variety of small organic molecules, called cofactors, coenzymes, or vitamins, have evolved to broaden the limited range of chemistry that can be catalyzed by simple proteins. 

The strength of ionic hydrogen bond (IHB) ranges from 5 to 35 kcal/mol. These strong interactions are implicated in ionic crystals and clusters, ion solvation, electrolytes, and acid base chemistry. The importance of this interaction in proton solvation, surface phenomenon, self-assembly process in supramo-lecular chemistry, and biomolecular structure and function has also been... 

The reduction of the pyrimidine to dihydropyrimidine is the reverse of the oxidation reaction carried out by DHODs. The structure of the FMN/pyrimidine-binding site is very similar to the structure of L. lactis DHODs. Three Asn residues form hydrogen bonds with the nitrogens and carbonyls of the pyrimidine analogous to DHODs. DPD has an active site cysteine proposed to act in acid/base chemistry similar to Class 1 DHODs. When mutated to alanine, only 1% of the wild-type activity was retained, indicating the importance of this residue in catalysis. Secondary tritium isotope effects using 5- H-uracil were determined in both H2O and D2O an inverse isotope effect was observed in H2O and the value became more inverse in D20. " This was taken as evidence of a stepwise mechanism in which hydride transfer to C6 is followed by protonation at C5. 

In contrast to inorganic molten salts, the fluidity of ionic hquids at room temperature permits their use as solvents for chemical reactions. Electrostatic properties and charge mobility in ionic hquids can play a distinctive role in chemical reactivity, as compared with neutral solvents. In particular, hydrogen and proton transfer reactions are likely to be sensitive to an ionic environment due to the hydrogen-bond acceptor ability of the anions. Such type of reactions are fundamental in acid-based chemistry and proton transport in solution. 

Although the importance of solvation effects for liquid-phase acid-base chemistry is evident, the experimental data are interpreted with difficulty.Thus, in aqueous solutions where the reference acid is H, ammonia is a stronger base than triethylphosphine, while the opposite is true when the reference Lewis acid is CH3Hg . Examples of reversal in acid-base strength were also found for gas-phase adduct formation, where interactions should be free of any solvent effect [14]. Several factors are responsible for these inversions, such as the ease of formation of multiple hydrogen bonds in aqueous solutions or the occurrence of favorably oriented orbitals that maximize the mutual overlap for gas-phase intermolecular interactions. 

Proton transfer from one molecule to another is one of the most studied phenomena in chemistry. It is the essence of acid-base chemistry. This process is related to hydrogen bonding, as a hydrogen-bonded complex can be an intermediate step ... 

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