Hydrogen bonding solute-solvent

Solvation can have a profound effect on the results of a chemical calculation. This is especially true when the solute and solvent are polar or when they can participate in hydrogen bonding. The solvent effect is expressed in several ways, including these ... 

For polar solutes and solvents, particularly those capable of hydrogen bonding, secondary solvent effects due to the specific nature of solute-solvent interactions may also have to be included in the model, since the ass imption that they are identical in the adsorbed and mobile phases, and therefore self-canceling, is no longer necessarily true. The addition of a secondary solvent term... 

Kemp et al., 1978). The rate is slowest in an aqueous solution and is enhanced in aprotic and/or dipolar solvents. The rate augmentation of 106—108 is attainable in dipolar aprotic solvents such as dimethyl sulfoxide and hexamethylphosphoramide (HMPA). Interestingly, the decarboxylation rate of 4-hydroxybenzisoxazole-3-carboxylate [53], a substance which contains its own protic environment, is very slow and hardly subject to a solvent effect (1.3 x 10-6 s-1 in water and 8.9 x 10-6 s-1 in dimethylformamide Kemp et al., 1975). The result is consistent with the fact that hydrogen-bonding with solvent molecules suppresses the decarboxylation. 

Kaznessis et al. [24] Solvent accessible surface area, hydrogen-bonding, solute dipole, molecular volume, etc. 

The values of the fractionation factors in structures [15]-[21] are not strictly comparable since they are defined relative to the fractionation in different solvent standards. However, in aqueous solution, fractionation factors for alcohols and carboxylic acids relative to water are similar and close to unity (Schowen, 1972 Albery, 1975 More O Ferrall, 1975), and it seems clear that the species [15]-[21] involving intermolecular hydrogen bonds with solvent have values of cp consistently below unity. These observations mean that fractionation of deuterium into the solvent rather than the hydrogen-bonded site is preferred, and this is compatible with a broader potential well for the hydrogen-bonded proton than for the protons of the solvents water, alcohol and acetic acid. 

Most linear ceilulosics may be dissolved in solvents capable of breaking the strong hydrogen bonds. These solvents include aqueous solutions of inorganic acids, zinc chloride, lithium chloride, dimethyl dibenzyl ammonium hydroxide, and cadmium or copper ammonia hydroxide (Schweizer s reagent). Cellulose is also soluble in hydrazine, dimethyl sulfoxide in the presence of formaldehyde, and dimethylformamide in the presence of lithium chloride. The product precipitated by the addition of nonsolvents to these solutions is highly amorphous and is called regenerated cellulose. 

Finally, with respect to the H-acceptor properties of the solvents (a-term), water and n-octanol are quite similar. Therefore, for a hydrogen-bonding solute like 4-BuPh, the corresponding product, a-(a), is close to zero. This is not the case for the hexadecane-water system where loss of hydrogen bonding in this alkane solvent causes both the H-acceptor and H-donor terms to contribute factors of about 100 to 4-BuPh s value of K. ... 

Addition of increasing amounts of triethylamine to a benzene solution of (9a) leads to a gradual shift of the equilibrium towards the enol form (9b). This can be interpreted in terms of hydrogen-bond formation between 9-anthranol and triethylamine. In hydrogen-bond accepting solvents such as A,A-dimethylformamide (enol content 56.5 cmol/mol at 20 °C), pyridine (58 cmol/mol), and dimethyl sulfoxide (61.5 cmol/mol), the anthranol content increases further [61, 134]. 

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