Question

Which of the following can undergo disproportionation reaction on heating with Conc. Alkali?

• A.

  

• B.

  

• C.

  

• D.

  

Hint:

Look for aldehydes with no alpha-hydrogens for Cannizzaro (disproportionation).
Typical example: \ch{HCHO}, \ch{C6H5CHO}.

Answer 1

The Correct Option is A

Aldehydes without an alpha-hydrogen undergo Cannizzaro reaction, which is a type of disproportionation reaction. \[ \text{Disproportionation: One molecule is reduced, another is oxidized.} \] In presence of conc. alkali: \[ 2\ch{C6H5CHO} \xrightarrow{NaOH} \ch{C6H5CH2OH} + \ch{C6H5COONa} \] Phenyl aldehyde (\ch{C6H5CHO}) lacks alpha-hydrogens, so it undergoes the Cannizzaro reaction. Other compounds: - \ch{C6H5COOH}, \ch{C6H5CH2OH}, \ch{C6H5CH3} do not undergo this reaction under same conditions.