H-bond acceptor basicity

R. H., Kamlet, M. J. Linear solvation relationships. 39. A multiple parameter equation for P values of (H-bond acceptor basicities) of the XYZP=0 compounds. /. Org. Chem. 1988, 53, 1737-1741. 

Fig. 4. Phase parameters (regression coefficients) for hydrophobicity (t)), n- and rc-electron activity (r), H-bond donor acidity (b), H-bond acceptor basicity (a), polarizability (s), and intercept (c) calculated using Eq. (5) from the retention data of 34 model compounds on 15 different stationary phases. Error bars indicate the confidence range at a 95% significance level (from [12]).

H hydrophobic interaction parameter 5 steric selectivity parameter A H-bond donor (acidity) parameter B H-bond acceptor (basicity) parameter C cation-exchange parameter (at dissociated silanols)... 

These equations make explicit the individual polar terms that are negatively related to lipophilicity and account for most polar interactions between a solute and the two solvent phases. In the case of the octanoi/water system (Eq. [6]), the main contributor to a solute s polarity is thus its H-bond acceptor basicity 0), and to a lesser extent its dipolarity/ polarizability (ir ). In contrast, the polar interactions expressed in alkane/ water partition coefficients (Eq. [7]) are the H-bond donor acidity (a) and the H-bond acceptor basicity 0), and again to a lesser extent the dipolarity/polarizability (ir ). 

The basic premise of Kamlet and Taft is that attractive solute—solvent interactions can be represented as a linear combination of a nonspecific dipolarity/polarizability effect and a specific H-bond formation effect, this latter being divisible into solute H-bond donor (HBD)-solvent H-bond acceptor (HB A) interactions and the converse possibility. To establish the dipolarity/polarizability scale, a solvent set was chosen with neither HBD nor HBA properties, and the spectral shifts of numerous solvatochromic dyes in these solvents were measured. These shifts, Av, were related to a dipolarity/polarizability parameter ir by Av = stt. The quantity ir was... 

The satisfactory correlations between Kamlet-Abraham s acidity parameters and H-bond donor free energy factors, and between Kamlet-Abraham s basicity parameters and H-bond acceptor free energy factors for many sets of compounds [26] deserve particular mentioning ... 

Various types of surface-anchor interactions are responsible for the adsorption of a dispersant to the particle surface. These include ionic or acid/base interactions sulphonic acid, carboxylic acid or phosphate with a basic surface (e.g., alumina) amine or quaternary with an acidic surface (e.g., silica) H-bonding surface esters, ketones, ethers, hydroxyls multiple anchors-polyamines and polyols (H-bond donor or acceptor) or polyethers (H-bond acceptor). Polarizing groups (e.g., polyurethanes) can also provide sufficient adsorption energies and, in nonspecific cases, lyophobic bonding (via van der Waals attractions) driven by insolubility (e.g., PMMA). It is also possible to use chemical bonding, for example by reactive silanes. 

More recently, Laurence et al. reported the development of the pA Hx H-bond basicity scale based on a set of 1338 experimental values related to 1164 HBAs [32], This approach uses the H-bonding free energies determined in CCl for a large number of chemically diverse H-bond acceptor molecules using 4-fluorophenol as the reference donor. The p bhx meaning similar to the log AT H-bond... 

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