Phenylephrine, an organic substance with molecular formula C9H13NO2, is used as a nasal decongenstant in over-thecounter medications. The molecular structure of phenylephrine is shown below using the usual shortcut organic structure. (c) Would you expect a solution of phenylephrine hydrochloride to be acidic, neutral, or basic?

Key Concepts

Acid-Base Chemistry

Acid-base chemistry involves the study of substances that can donate protons (acids) or accept protons (bases). The pH scale measures the acidity or basicity of a solution, with values below 7 indicating acidity, 7 being neutral, and above 7 indicating basicity. Understanding the nature of the solute and its ability to donate or accept protons is crucial for predicting the pH of a solution.

Ionization of Phenylephrine

Phenylephrine contains a hydroxyl group (-OH) and an amine group (-NH), which can influence its behavior in solution. When phenylephrine is dissolved in water, it can undergo ionization, where the amine group can accept a proton, forming a positively charged ion. This ionization is key to determining whether the resulting solution is acidic, neutral, or basic.

Phenylephrine Hydrochloride

Phenylephrine hydrochloride is the hydrochloride salt form of phenylephrine, which is often more soluble in water than its base form. The presence of the hydrochloride ion (Cl-) can affect the overall pH of the solution. Typically, salts formed from weak bases and strong acids tend to create acidic solutions, which is an important consideration when evaluating the acidity of phenylephrine hydrochloride.