What is the product of the following reaction?

The correct answer is Option (1) → m-Nitrobenzaldehyde

The given reaction involves nitration of benzaldehyde using a mixture of concentrated nitric acid and concentrated sulphuric acid, which is known as the nitrating mixture.

This mixture generates the nitronium ion (NO₂⁺), which acts as the electrophile in the electrophilic aromatic substitution reaction.

Formation of electrophile:

HNO₃ + H₂SO₄ → NO₂⁺ + HSO₄⁻ + H₂O

The nitronium ion (NO₂⁺) then attacks the aromatic ring.

Directing effect of –CHO group

The –CHO (aldehyde) group is:

• Electron withdrawing due to the −I effect and −M effect
• Deactivating toward electrophilic substitution

Because of this electron-withdrawing nature, the –CHO group directs incoming electrophiles to the meta position.

Thus nitration of benzaldehyde predominantly gives:

m-Nitrobenzaldehyde

Option-wise Explanation

Option 1: m-Nitrobenzaldehyde

The –CHO group is a meta-directing deactivating group, so nitration occurs mainly at the meta position relative to the aldehyde group. Therefore this option is correct.

Option 2: p-Nitrobenzaldehyde

Although para substitution is possible with activating groups, the –CHO group strongly deactivates the ortho and para positions, making meta substitution preferred. Hence this option is incorrect.

Option 3: m-Sulphonatobenzaldehyde

Sulphonation would require fuming sulphuric acid (SO₃ / H₂SO₄), not nitric acid. Since the reaction conditions indicate nitration, this option is incorrect.

Option 4: Benzoic acid

Benzoic acid would be formed by oxidation of the aldehyde group, not by nitration. Therefore this option is incorrect.