Question

Which of following reagents is used to avoid further oxidation of aldehydes?

• A. \( \mathrm{C_5H_5NH^+CrO_3Cl} \)
• B. \( \mathrm{K_2Cr_2O_7/dil.\ H_2SO_4} \)
• C. dil.\ \( \mathrm{HNO_3} \)
• D. \( \mathrm{CrO_3} \)

Hint:

PCC is a selective oxidising agent that prevents over-oxidation of aldehydes.

Answer 1

The Correct Option is A

Step 1: Understanding the problem.
Aldehydes are easily oxidised to carboxylic acids by strong oxidising agents. To stop oxidation at the aldehyde stage, a mild and selective oxidising reagent is required.

Step 2: Identifying the reagent.
Pyridinium chlorochromate (PCC), represented as \( \mathrm{C_5H_5NH^+CrO_3Cl} \), is a mild oxidising agent that oxidises alcohols to aldehydes without further oxidation.

Step 3: Eliminating other options.
Potassium dichromate, nitric acid, and chromium trioxide are strong oxidising agents and oxidise aldehydes further to carboxylic acids.

Step 4: Conclusion.
Thus, PCC is used to avoid further oxidation of aldehydes.