Acetaminophen, also known as paracetamol, does not act as a base in water due to its chemical structure and the presence of functional groups that do not readily donate electrons. In aqueous solutions, a base is typically a substance that can accept protons (H+) or donate a pair of valence electrons. Acetaminophen, with its amide group, does not have significant basic properties, making it largely neutral in such environments.
On the other hand, p-aminophenol has an amine (-NH2) group that is more basic. This amine can easily accept a proton, allowing p-aminophenol to act as a base in water. The lone pair of electrons on the nitrogen atom can readily interact with protons, giving rise to its basic properties.
In summary, the distinction in basicity between acetaminophen and p-aminophenol stems from their functional groups, with the amine group in p-aminophenol facilitating proton acceptance, while acetaminophen’s amide group does not contribute to basic behavior in an aqueous setting.