See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the substrates and products: - The first substrate is 2-propanol (a secondary alcohol). PCC oxidizes secondary alcohols to ketones. So (A) = acetone (propan-2-one), a ketone. - The second substrate is 1-propanol (a primary alcohol). PCC oxidizes primary alcohols to aldehydes (stops at aldehyde, does not over-oxidize to carboxylic acid). So (B) = propanal, an aldehyde. Step 2 - Identify a reagent that differentiates a ketone from an aldehyde: - (a) NaH: NaH is a base/reducing agent used for deprotonation of acidic protons. It does not specifically differentiate aldehydes from ketones. - (b) 2,4-DNA (2,4-dinitrophenylhydrazine, Brady's reagent): This reagent reacts with BOTH aldehydes AND ketones (any carbonyl compound) to form orange/yellow precipitates. It cannot differentiate between the two. - (c) Tollen's reagent (ammoniacal silver nitrate): Tollen's reagent selectively oxidizes aldehydes to carboxylates, producing a silver mirror (positive test), while ketones do NOT react with Tollen's reagent. Therefore, (B) propanal gives a silver mirror with Tollen's reagent, while (A) acetone does not. This clearly differentiates the two compounds. - (d) NaHSO3: Sodium bisulfite forms addition products with aldehydes and methyl ketones (and some cyclic ketones). Both acetone (a methyl ketone) and propanal (an aldehyde) react with NaHSO3, so it cannot reliably differentiate them in this case. Step 3 - Conclusion: Tollen's reagent uniquely distinguishes aldehydes (positive silver mirror test) from ketones (no reaction), making it the correct reagent to differentiate (A) acetone from (B) propanal. Therefore, the correct answer is C.