Nitrogen-hydrogen bond parameters

For hydrogen-bonding parameters we have used h> the number of OH and/or NH bonds in the substituent, and n , the number of lone pairs on oxygen and/or nitrogen atoms The use of these parameters is based on the argument that if one of the phases... 

Hydrogen bond formation between dissimilar molecules is an example of adduct formation, since the hydrogen atom that is bonded to an electronegative atom, such as oxygen or nitrogen, is a typical acceptor atom. The ability of molecules to donate a hydrogen bond is measured by their Taft-Kamlet solvatochromic parameter, a, (or a . for the monomer of self-associating solutes) (see Table 2.3). This is also a measure of their acidity (in the Lewis sense, see later, or the Brpnsted sense, if pro tic). Acetic acid, for instance, has a = 1.12, compared with 0.61 for phenol. However, this parameter is not necessarily correlated with the acid dissociation constant in aqueous solutions. 

Solubility is a function of many molecular parameters. Ionization, molecular structure and size, stereochemistry, and electronic structure all influence the basic interactions between a solvent and solute. As discussed in the previous section, water forms hydrogen bonds with ions or with polar nonionic compounds through -OH, -NH, -SH, and -C=0 groups, or with the nonbonding electron pairs of oxygen or nitrogen atoms. The ion or molecule will thus acquire a hydrate envelope and separate from the bulk solid that is, it dissolves. The interaction of nonpolar compounds with lipids is based on a different phenomenon, the hydrophobic interaction, but the end result is the same formation of a molecular dispersion of the solute in the solvent. 

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