Question

Acetic acid on heating in presence of $P_2O_5$ gives

• A. No reaction
• B. peracid
• C. acetylene
• D. acetic anhydride

Answer 1

Answer: (D)

acetic anhydride

Answer 2

When acetic acid ($CH_3COOH$) is heated in the presence of phosphorus pentoxide ($P_2O_5$), $P_2O_5$ acts as a strong dehydrating agent. Carboxylic acids undergo intermolecular dehydration when heated with dehydrating agents like $P_2O_5$ to form acid anhydrides.

The reaction is as follows:

$2 \text{CH}_3\text{COOH} \xrightarrow{\text{P}_2\text{O}_5, \Delta} (\text{CH}_3\text{CO})_2\text{O} + \text{H}_2\text{O}$

Here, two molecules of acetic acid lose one molecule of water to form acetic anhydride.