Hydrogen bond acidity/basicity

Murray,). S., Politzer, P. Relationships between solute hydrogen-bond acidity/ basicity and the calculated electrostatic potential./. Chem. Res. (S) 1992,... 

Hagelin, J., T. Brinck, M. Berthelot, J. S. Murray, and P. Politzer. 1995. Family Dependent Relationships Between Computed Molecular Surface Quantities and Solute Hydrogen Bond Acidity/Basicity and Solute-Induced Methanol O-H Infrared Frequency Shifts. Can. J. Chem. 73, 483. 

Abraham et at. [2], [3], [4] Solubility, excess molar refraction, polarizability, hydrogen-bond acidity/basicity, and McGowan volume... 

H. Hagelin et al., Family-independent relationships between computed molecular surface quantities and solute hydrogen bond acidity/basicity and solute-induced methanol O-H infrared frequency shifts. Can. J. Chem. 73, 483 188 (1995)... 

Abraham et al. (1999) generated a QSAR equation for the permeation of 47 aqueous solutes across human skin. This demonstrated that dermal permeability increased with increasing molar refraction and McGowan volume and decreased as hydrogen bond acidity, basicity, and dipolar-ity/polarizability increased. 

Tfaeie have been a number of attempts to develop solvent parameter scales that could be used to correlate ttiermodynamic and kinetic results in terms of these patametois. Gutmann s Donor Numbers, discussed previously, are sometimes used as a solvent property scale. Kamlet and Taft and co-workers developed the solvatochromic parameters, Uj, B, and n that are related to the hydrogen bonding acidity, basicity and polarity, respectively, of the solvent. Correlations with these parameters also use the square of tte Hildebrand solubility parameter, (5, that gives the solvent cohesive energy density. Parameters for some common solvents are collected in Table 3.6. 

Where SP is a solvation p>arameter related with the free energy change such as gas-liquid partition coefficient, specific retention volume or adjusted retention time at a given temperature. The capital letters represent the solutes properties and the lower case letters the complementary properties of the ionic liquids. The solute descriptors are the excess molar refraction E, dipolarity/ polarizability S, hydrogen bond acidity basicity, A and B, respectively, and the gas-liquid partition coefficient on n-hexadecane at 298 K, L. The solute... 

Where FCl is the solute gas-liquid partition coefficient, r is the tendency of the solvent to interact through k- and n-electron pairs (Lewis basicity), s the contribution from dipole-dipole and dipole-induced dipole interactions (in molecular solvents), a is the hydrogen bond basicity of the solvent, b is its hydrogen bond acidity and I is how well the solvent will separate members of a homologous series, with contributions from solvent cavity formation and dispersion interactions. 

The difference in the hydrogen bond acidities and basicities was far more marked. The a value is largely determined by the availability of hydrogen bond donor sites on the cation. Values range from 0.8-0.9 for the monoalkylammonium salts, and are slightly lower (0.3-0.8) for the imidazolium salts. In the absence of a... 

The correlation of Snyder s solvent strength e° with molecular dipolarity and polarizability (7t ) and the hydrogen-bond acidity (a) and the hydrogen-bond basicity ((3) solvatochromic parameters for adsorption chromatography can be achieved, although most papers on solvatochromic parameters deal with reversed-phase systems [18]. 

Overall, we have shown that family-independent correlations can be obtained for solute hydrogen bond acidity and basicity, as quantitated by a 1 and log KHB. These are well represented at the HF/6-31G level by an electrostatic potential term alone, V or V, . , respectively (Hagelin et al. 1995). 

Polymer (dry) Hydrogen bond acidity Hydrogen bond basicity Polarizability Et (30)... 

In an excellent paper, Zhao et al. [29] assembled a carefully reviewed literature set of human absorption data on 241 drugs. They showed that a linear regression model built with 5 Abraham descriptors could fit percent human absorption data reasonably well (r2 = 0.83, RMSE = 14%). The descriptors are excess molar refraction (E), polarizability (S), hydrogen bond acidity (A), hydrogen bond basicity (B), and McGowan volume (V), all related to lipophilicity, hydrophilicity, and size. In a follow-on paper, data on rat absorption for 151 drugs was collected from the literature and modeled using the Abraham descriptors [30]. A model with only descriptors A and B had r2 = 0.66, RMSE = 15%. 

The parameters a and p indicate the capacity of a solvent to donate or accept a hydrogen bond from a solute, i.e., the solvent s hydrogen bond acidity or basicity. % is intended to reflect van der Waals-type solute-solvent interactions (dipolar, dispersion, exchange-repulsion, etc.). Equation (43) was subsequently expanded to include a term representing the need to create a cavity for the solute (and thus to interrupt solvent-solvent interactions).188 For this purpose was used the Hildebrand solubility parameter, 5, which is defined as the square root of the solvent s energy of vaporization per unit volume.189 Thus Eq. (43) becomes,190... 

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