The unsaturated ether on acidic hydrolysis produces carbonyl compounds as shown below :- [figure] Based on this, predict the solution/reagent that will help to distinguish "P" and "Q" obtained in the following reaction :- CH3-CH=CH-O- CH3 |C=CH2 [ ]H3O P + Q
- Saturated NaHSO3 solution
- Fehling solution
- Lucas reagent
- 2,4-DNP reagent
Answer
(2) Fehling solution
Solution
Each O–vinyl bond is hydrolysed and the vinyl carbon becomes a carbonyl carbon:
CH3-CH=CH-O- CH3 |C=CH2 [ ]H3O
CH3-CH2-CHO + CH3- O \|C-CH3
P = propanal (aldehyde), Q = propanone (ketone).
(1) Both an aldehyde and a methyl ketone form bisulphite addition products no distinction.
(2) Fehling solution: propanal gives a red-brown precipitate of Cu2O, propanone does not distinguishes.
(3) Lucas reagent is a test for alcohols neither responds.
(4) 2,4-DNP gives orange-yellow 2,4-DNP derivatives with both no distinction.
Answer: (2)