Question

When m-chlorobenzaldehyde is treated with 50% KOH solution, the product(s) obtained is (are) 

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

When m-chlorobenzaldehyde is treated with a 50% KOH solution, the reaction that occurs is the Cannizzaro reaction. This is a redox reaction wherein aldehydes without alpha hydrogens undergo simultaneous oxidation and reduction to form a carboxylic acid and an alcohol.

Let's analyze what happens in this reaction:

1. m-Chlorobenzaldehyde lacks alpha hydrogens, making it a suitable candidate for the Cannizzaro reaction.
2. In the Cannizzaro reaction, one molecule of the aldehyde undergoes oxidation to form a carboxylic acid, while another molecule reduces to form an alcohol.
3. For m-chlorobenzaldehyde, the oxidation product is m-chlorobenzoic acid, and the reduction product is m-chlorobenzyl alcohol.

The balanced chemical reaction is as follows:

\text{2 C}_6\text{H}_4\text{Cl-CHO} + \text{KOH} \rightarrow \text{C}_6\text{H}_4\text{Cl-COONa} + \text{C}_6\text{H}_4\text{Cl-CH}_2\text{OH}\

where:

• \text{C}_6\text{H}_4\text{Cl-CHO}\ is m-chlorobenzaldehyde.
• \text{C}_6\text{H}_4\text{Cl-COONa}\ is the sodium salt of m-chlorobenzoic acid.
• \text{C}_6\text{H}_4\text{Cl-CH}_2\text{OH}\ is m-chlorobenzyl alcohol.

Hence, one of the products obtained is m-chlorobenzyl alcohol.

The correct option is:

Therefore, the product(s) obtained when m-chlorobenzaldehyde is treated with 50% KOH solution is m-chlorobenzyl alcohol.