How do I predict the solubility of a compound in a mixture of water and an organic co-solvent?

Question

I'm trying to predict the solubility of long alcohols (e.g. 1-octanol, 1-decanol or 1-dodecanol) in a mixture of water and an organic co-solvent such as DMSO, acetonitrile or ethyl acetate. For example, decanol in water with 25% DMSO or saturated with ethyl acetate (8.3%). I of course know the solubility of alcohols in water, but not in organic solvents or in mixtures. I found a server to predict the solubility of any compound in any solvent, but I'm not sure how accurate it is and it only does predictions for pure solvents, not mixtures: http://showme.physics.drexel.edu/onsc/models/multisolvent.php Any input on this would be greatly appreciated!

Answer 1

Like dissolves like. I can't provide a formula for such a question. However, alcohols dissolve well in water for the same reason that they don't dissolve well in organic solvents. The ability to lose an H+ allows dissociation in water. However, as the chain length increases in hydrocarbons (organic, non-polar components) and the molecule becomes less and less soluble in water and more and more soluble in something organic like DMSO.

So dodecanol has a higher solubility in DMSO than ethanol, but ethanol has a higher solubility in water than dodecanol.