Question

Which of the following reagent cannot be used to oxidize primary alcohols to aldehydes?

• A. Pyridinium chloro chromate
• B. Heating in presence of Cu at $573$K
• C. $KMn{O}_4$ in acidic medium
• D. $Cr{O}_3$ in anhydrous medium

Answer 1

Answer: (C)

$KMn{O}_4$ in acidic medium

$KMn{O}_4$ in acidic medium cannot be used to oxidize primary alcohols to aldehydes. The oxidation will not stop at aldehyde stage. It will further continue to carboxylic acid. To stop oxidation at aldehyde stage, we need mild oxidising agent such as PCC or PDC is used.