Relationship between Ionization and Lipophilicity

The general form of the equation for lipophilicity profiles is shown below [Pg.24]

In this equation, Dp[H] represents the distribution coefficient at a particular pH, and may also be expressed as [Pg.24]

Log D for the ionized form will depend on conditions of solution. [Pg.24]

The term p[H] represents the pH value of the solution expressed on a concentration scale [5], where [H] represents the concentration of hydrogen ions H+. P° represents the partition coefficient of the unprotonated species, P1 is the mono-protonated species, and so on. P may also be expressed as [Pg.25]

The widely used term log P refers to the logarithm of the partition coefficient P of the unionized species, which is P° for a base with no acidic functions, and P1 for a monoprotic acid or an ordinary ampholyte. Log P is equal to log D at any pH remote from the pKa where the molecule exists entirely in its unionized form. Log D at any pH is equal to log P for a non-ionizable molecule. [Pg.25]

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