Hybrid solvation hydrogen bonds/bonding

Hybrid solvation Implicit solvation plus Explicit solvation microsolvation subjected to the continuum method. Here the solute molecule is associated with explicit solvent molecules, usually no more than a few and sometimes as few as one, and with its bound (usually hydrogen-bonded) solvent molecule(s) is subjected to a continuum calculation. Such hybrid calculations have been used in attempts to improve values of solvation free energies in connection with pKp. [42], and also [45] and references therein. Other examples of the use of hybrid solvation are the hydration of the environmentally important hydroxyl radical [52] and of the ubiquitous alkali metal and halide ions [53]. Hybrid solvation has been surveyed in a review oriented toward biomolecular applications [54]. 

In the case of solvents with a low solvating power, in which protonated or deprotonated species are not free from counterion effects, spectroscopic and thermodynamic parameters associated with hydrogen bonding or Lewis acid-base interactions can be usefully related to PA or GB. Kamlet and coworkers reported linear relationships for five series of bases with sp - and sp -hybridized oxygen and sp-, sp - and sp -hybridized nitrogen. At the same time, Zeegers-Huyskens presented the relationships " reported in Figure 2. 

The water molecule is composed of two hydrogen atoms covalently bonded to an oxygen atom with tetrahedral (sp3) electron orbital hybridization. As a result, two lobes of the oxygen sp3 orbital contain pairs of unshared electrons, giving rise to a dipole in the molecule as a whole. The presence of an electric dipole in the water molecule allows it to solvate charged ions because the water dipoles can orient to form energetically favorable electrostatic interactions with charged ions. 

This pK a is higher than would be anticipated for ortho- and meta- substituted phenols since the o meth-oxyphenol has a pK a of 9.98, m-methoxyphenol a pK a of 9.65 and resorcinol a pK a of F.81 (13). A molecular model of the drug shows that the free rotation of the phenolic hydrogen is hindered by the A -hydrogen and can explain a9-tetrahydrocannabinol s higher pK a. Of course, if solvated dimers, trimers, etc., exist with hydrophobic bonding, the observed pK a could be a hybrid pK a for a solution of such polymers. 

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