Is octanoic acid more soluble in \(1 M \mathrm{HCl}, 1 M \mathrm{NaOH}\) , or pure water? Explain. Drugs such as morphine $\left(\mathrm{C}_{17} \mathrm{H}_{19} \mathrm{NO}_{3}\right)$ are often treated with strong acids. The most commonly used form of morphine is morphine hydrochloride \(\left(\mathrm{C}_{17} \mathrm{H}_{20} \mathrm{ClNO}_{3}\right)\) Why is morphine treated in this way? (Hint: Morphine is an amine.)

Octanoic acid, also known as caprylic acid, has the chemical formula \(\mathrm{C}_{8} \mathrm{H}_{16} \mathrm{O}_{2}\). It is a medium-length carboxylic acid with a hydrocarbon chain containing 8 carbon atoms. It is a weak acid that can donate one hydrogen ion, and its conjugate base is the octanoate ion (\(\mathrm{C}_{8}\mathrm{H}_{15}\mathrm{O}_{2}^{-}\)).

The solubility of octanoic acid depends on how well it can dissociate and form ions in different solutions. Since octanoic acid is a weak acid, it can donate a proton (H+) and form its conjugate base, the octanoate ion. In a \(1 M \mathrm{HCl}\) solution, the strong acid (HCl) will already have dissociated to form a high concentration of H+ ions, so there will be no significant increase in H+ ions if the octanoic acid was dissolved in it. In a \(1 M \mathrm{NaOH}\) solution, NaOH will dissociate to form a high concentration of OH− ions, which can neutralize protons (H+) from octanoic acid. This reaction produces water molecules and increases octanoic acid solubility. In pure water, the solubility of octanoic acid is very low because of its non-polar hydrocarbon chain. At room temperature, water can only dissolve approximately 0.3 g octanoic acid in 100 g of water due to its hydrophobic nature.

Comparing the solubilities of octanoic acid in the three solutions, we can conclude that octanoic acid is more soluble in \(1 M \mathrm{NaOH}\) than in \(1 M \mathrm{HCl}\) or pure water due to the neutralization of protons (H+) by the hydroxide ions (OH−) present in the NaOH solution.

Morphine is an amine, having a nitrogen atom with lone pair electrons that can accept protons and form a more water-soluble salt. Morphine's chemical structure includes a nitrogen atom, and its chemical formula is \(\mathrm{C}_{17}\mathrm{H}_{19}\mathrm{NO}_{3}\). The reaction of morphine with hydrochloric acid (HCl) results in the formation of morphine hydrochloride salt, with the chemical formula \(\mathrm{C}_{17}\mathrm{H}_{20}\mathrm{ClNO}_{3}\).

Morphine is treated with hydrochloric acid because, as an amine, it can react with the acid to form a salt. This salt, morphine hydrochloride, is much more soluble in water than morphine itself, making it easier to be administered in medical applications. The improved solubility is due to the positive charge on the nitrogen atom in morphine hydrochloride, which allows it to interact more effectively with the polar water molecules.