Question

The unsaturated ether on acidic hydrolysis produces carbonyl compounds as shown below. Based on this, predict the solution/reagent that will help to distinguish "P" and "Q" obtained in the reaction.

• A. 2,4-DNP reagent
• B. Saturated NaHSO$_3$ solution
• C. Fehling solution
• D. Lucas reagent

Hint:

Fehling’s test is specific for aliphatic aldehydes.

Answer 1

The Correct Option is C

To distinguish between two carbonyl compounds, typically aldehydes and ketones, specific reagents are used. Here, we need to identify which reagent can distinguish "P" and "Q" produced from the hydrolysis of an unsaturated ether.

• 2,4-DNP Reagent: This reagent identifies carbonyl groups by forming a yellow-orange precipitate. However, it cannot distinguish between aldehydes and ketones as both will react similarly.
• Saturated NaHSO₃ Solution: This reacts typically with aldehydes, especially larger ketones, to form soluble bisulfite addition compounds. Though it can sometimes distinguish between certain types of aldehydes and ketones, it is not as reliable for this task.
• Fehling Solution: This reagent is a key test for distinguishing aldehydes from ketones. Aldehydes reduce the copper(II) ions in Fehling's solution to form a red precipitate of copper(I) oxide, while ketones (those without α-hydrogen) do not react.
• Lucas Reagent: This reagent is used for differentiating alcohols based on their reactivity in substitution reactions and is irrelevant to carbonyls.

Based on the explanation above, Fehling solution is the correct answer. It distinguishes "P" and "Q" because Fehling's solution reacts with aldehydes to form a red precipitate, while most ketones do not undergo this reaction.