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Ibuprofen (C13H18O2) is a weakly acidic molecule with a pKa =
4.9. It has an estimated solubility of 0.021 mg/mL at 20 °C and a
log P = 3.83 [M(C) = 12.01 g/mol; M(O) = 16.00 g/mol].
(a) Determine the pH of a 18 mg/L aqueous solution of ibuprofen
in pure water.
(b) If 18 mg/L aqueous solution of ibuprofen was prepared using
0.5 M NaCl solution. Would you expect the pH of the solution to be
different? If so, how? Provide reasons to support your answer.
(c) What percentage of ibuprofen will be ionised: (i) in a pH
5.0 solution and (ii) a pH 7.8 solution.
(d) Determine the total solubility of ibuprofen at a pH of
7.8.
(e) The solubility of ibuprofen increases with increasing
solution pH. Briefly explain why this occurs.
(f) The aqueous solubility of ibuprofen is very low (0.021 mg/mL
at 20 °C). Describe three ways in which you could try to formulate
an ibuprofen liquid dosage form with a higher concentration of
ibuprofen.
"ОН Ibuprofen