Distribution Coefficient and Log D
The distribution coefficient is the ratio of the sum of the concentrations of all forms of the compound (ionized plus un-ionized) in each of the two phases. For measurements of distribution coefficient, the pH of the aqueous phase is buffered to a specific value such that the pH is not significantly perturbed by the introduction of the compound. The logarithm of the ratio of the sum of concentrations of the solute's various forms in one solvent, to the sum of the concentrations of its forms in the other solvent is called Log D:
In addition, log D is pH dependent, hence one must specify the pH at which the log D was measured. Of particular interest is the log D at pH = 7.4 (the physiological pH of blood serum).
For un-ionizable compounds, log P = log D at any pH.
Read more about this topic: Partition Coefficient
Famous quotes containing the words distribution and/or log:
“In this distribution of functions, the scholar is the delegated intellect. In the right state, he is, Man Thinking. In the degenerate state, when the victim of society, he tends to become a mere thinker, or, still worse, the parrot of other mens thinking.”
—Ralph Waldo Emerson (18031882)
“There is hardly a pioneers hut which does not contain a few odd volumes of Shakespeare. I remember reading the feudal drama of Henry V for the first time in a log cabin.”
—Alexis de Tocqueville (18051859)