A useful method for assessing the extent of the partitioning of a drug between the bloodstream and body fat is to determine the infinite dilution partition coefficient for the drug between water and n-octanol:

Kdrug = xdrug in n-octanol-rich phase / xdrug in water-rich phase

For a drug 3-(4-ethyl phenyl)propanoic acid (the structure is below),

 

a. Use UNIFAC to determine the mutual solubility of water + n-octanol at the body temperature 37°C.

b. Use UNIFAC to determine the infinite dilution partition coefficient at the body temperature 37°C.

c. Will the drug stay in the bloodstream or move into fatty body parts?