See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The compound shown is a vinyl ether (an enol ether). Looking at the structure, the left side shows a trans (E) alkene with a methyl group (CH3-CH=CH-) connected via oxygen to a gem-dimethyl vinyl group (-O-C(CH3)=CH2). This is (E)-1-propenyl 2-methylallyl ether, or more precisely, the ether between (E)-prop-1-en-1-ol (as enol) and 2-methylallyl group. Step 2 - Acid hydrolysis of enol ethers: Under H3O+ conditions, enol ethers undergo hydrolysis. The enol ether linkage (C=C-O-C) hydrolyzes to give a carbonyl compound plus an alcohol. Step 3 - Products A and B: - The (E)-1-propenyl part (CH3-CH=CH-O-) is an enol ether that on hydrolysis gives propanal (CH3CH2CHO) - an aldehyde. - The 2-methylallyl part (-O-C(CH3)=CH2) on hydrolysis gives acetone (CH3COCH3) - a ketone. So A = propanal (an aldehyde) and B = acetone (a ketone), or vice versa. Step 4 - Differentiating the products: - (a) 2,4-DNP: Both aldehydes and ketones react with 2,4-DNP to give orange/yellow precipitates. Cannot differentiate between an aldehyde and a ketone using this reagent. - (b) Fehling solution: Fehling's solution is a reagent that distinguishes aldehydes from ketones. Aliphatic aldehydes (like propanal) reduce Fehling's solution giving a brick-red precipitate of Cu2O, while ketones (like acetone) do not react. This CAN differentiate A from B. - (c) Lucas reagent (ZnCl2/conc. HCl): This differentiates primary, secondary, and tertiary alcohols. Neither propanal nor acetone is an alcohol, so Lucas reagent is not applicable here. - (d) NaHSO3: Both aliphatic aldehydes and methyl ketones (like acetone) form bisulfite addition products with NaHSO3. Acetone does react with NaHSO3, and so does propanal, so this cannot reliably differentiate them in this context. Step 5 - Conclusion: Fehling's solution can differentiate an aliphatic aldehyde (propanal gives positive test) from a ketone (acetone gives negative test), making option (b) the correct answer. Therefore, the correct answer is B.