Hydrogen-bond basicity, solvation effects

When a solute is dissolved in a pure hydrogen-bond donor solvent, such as water or alcohol, all acceptor sites are involved in the solvation phenomenon. For example, the partition of phenols between water and organic phases now depends both on the oxygen and on the tt hydrogen-bond basicities, because of the excess of water molecules. From sets of water-solvent partition coefficients, Abraham has constructed a scale of effective or summation hydrogen-bond basicity, for about 350 solutes, of which... 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

The accurate determination of gas-phase basicities and gas-phase acidities opened the way to analyses of the effect of solvation on proton acidities, and on hydrogen-bond acidities and basicities, as well as on substituents effects. 

NO2, 3-NO2, 4-Br, 4-Ph, 4-Me, 4-MeCONH, and 4-MeO, log = 4.56, 5.06, 4.46, 4.49, 2.08, 4.00, 0.67 and 2.47, respectively) show that in solution the open-chain tautomer 42A is strongly stabilized by solvation effects. An increase in the polarity and polarizability of the solvent shifts the equilibrium toward the open-chain tautomer (y < 0, p < 0). The higher polarity of the open-chain tautomer may be caused by intramolecular hydrogen bonds, as shown in 43 or 44. An increase in the general basicity of the... 

A solvent, in addition to permitting the ionic charges to separate and the electrolyte solution to conduct an electrical current, also solvates the discrete ions, by ion-dipole or ion-induced dipole interactions and by more direct interactions, such as hydrogen bonding to anions or electron-pair donation to cations. Lewis acidity and basicity of the solvents affect the latter. The redox properties of the ions at an electrode depend on their being solvated, and the solvation effects electrode potentials or polarographic half-wave potentials. 

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