In the reaction p-aminophenol + acetic anhydride --> acetaminophen , 4.5 ml of water is added into the flask with the p-aminophenol and acetic anhydride at the beginning of the experiment. What is the purpose of this water?

Do you suppose it converts the acetic anhydride to acetic acid?

the reaction p-aminophenol + acetic anhydride --> acetaminophen , 4.5 ml of water is added into the flask with the p-aminophenol and acetic anhydride at the beginning of the experiment. What is the purpose of this water?

The purpose of adding 4.5 mL of water at the beginning of the experiment in the reaction between p-aminophenol and acetic anhydride to form acetaminophen is to facilitate the reaction and ensure efficient mixing of the reactants. Water serves as a medium to dissolve and solvate the reactants, allowing them to come into closer contact and react more readily. It also helps to control the reaction conditions and prevent the formation of undesired by-products.

The purpose of adding water in this reaction is to hydrolyze the acetic anhydride.

Acetic anhydride (C4H6O3) is a reagent commonly used in acetylation reactions. It reacts with the hydroxyl group (-OH) present in p-aminophenol (C6H7NO) to form acetaminophen (C8H9NO2), which is the desired product. However, acetic anhydride contains two acetyl groups (C2H3O) that can react with the hydroxyl group, resulting in the formation of a diacetyl compound instead of acetaminophen.

To prevent the formation of diacetyl and promote the formation of acetaminophen, a small amount of water is added to the reaction mixture. Water acts as a nucleophile and attacks the acetic anhydride, leading to its hydrolysis. This hydrolysis breaks down the acetic anhydride into acetic acid (CH3COOH), which is less reactive towards the p-aminophenol. As a result, the acetic acid does not interfere with the desired acetylation reaction, ensuring the formation of acetaminophen.

In summary, the addition of water helps control the reaction by hydrolyzing the acetic anhydride, preventing unwanted side reactions and promoting the formation of acetaminophen.