Alkanals can be distinguished from alkanones by reaction with

Correct answer: Fehling’s solution.

Explanation: Alkanals (aldehydes) are readily oxidized and will reduce Fehling’s solution (Cu²⁺ complex in alkaline medium) to a brick-red precipitate of Cu₂O. Alkanones (ketones) generally do not react, so the solution stays blue—this distinguishes the two.

• Sudan III stain – Lipid/fat stain; not a test for carbonyl class.
• Starch iodide paper – Detects oxidizing agents (liberated iodine gives blue-black); not a specific aldehyde/ketone test.
• Lithium tetrahydridoaluminate(III) (LiAlH₄) – Reduces both aldehydes and ketones to alcohols; cannot distinguish them.
• Fehling’s solution – Correct: aldehydes give brick-red Cu₂O; ketones do not.