In the reaction between p-aminophenol and acetic anhydride to form acetaminophen, what was the purpose of adding water to the reaction mixture? There are a couple of possible answers, and this requires a detailed explanation for credit.
thanks!
In the reaction between p-aminophenol and acetic anhydride to form acetaminophen, the addition of water serves multiple purposes:
1. Hydrolysis of acetic anhydride: Acetic anhydride is a reactive compound commonly used as an acetylating agent in organic synthesis. By adding water to the reaction mixture, hydrolysis of acetic anhydride occurs. This means that the water molecules attack the acetic anhydride, breaking it down into acetic acid molecules. This step is important because it allows the acetylating agent to be converted into acetic acid, which is less reactive and less likely to react with other components in the reaction mixture.
2. Protonation of aminophenol: The addition of water provides a source of protons (H+ ions), which can protonate the p-aminophenol molecule. The p-aminophenol molecule contains an amino group (NH2) that can act as a nucleophile. However, nucleophilic substitution reactions are typically slow in the absence of a catalyst. By protonating the amino group with water, the reaction rate is increased because the positive charge on the amino group makes it more susceptible to nucleophilic attack.
3. Favoring the formation of acetaminophen: The hydrolysis of acetic anhydride and the protonation of p-aminophenol both contribute to the formation of acetaminophen. Acetaminophen is formed when the acetyl group (CH3CO-) from acetic anhydride is transferred to the amino group of p-aminophenol, resulting in a new amide bond (NHCOCH3). By facilitating the hydrolysis of acetic anhydride and protonation of p-aminophenol, water promotes the reaction towards the formation of acetaminophen.
To summarize, water is added to the reaction mixture in the synthesis of acetaminophen to hydrolyze the acetic anhydride, protonate the p-aminophenol, and promote the formation of acetaminophen. These steps enhance the reaction rate and improve the yield of the desired product.