Given that the structures of cocaine (on the right side of the equation) and its free base ( on the left side) with an H+ :

Question

a. Would you expect K for the cocaine to be greater or less than 1.0? Explain.
b. Would K for the free base be higher or lower than for cocaine? Explain.
c. If you were going to extract cocaine into dichloromethane (an immiscible organic solvent) from
an aqueous solution, would you make the aqueous solution acidic or basic? Explain why.

Answer 1

a) You would expect K>1 because cocaine is in the presence of an acid, which raises K (low pH = high K value)
b) Base = high pH, so you would expect K to be lower.
c) You would want to make the aqueous solution basic because then more cocaine would enter the aqueous layer (k=aq/non-aq), allowing for more cocaine to be extraced.