See image — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the key structural differences among the three compounds: - p-ethyl phenol: has a phenolic OH (acidic, reacts with FeCl3 to give purple/violet color) - p-methyl anisole: has an ether linkage (OCH3), no free OH group, unreactive with FeCl3 and does not oxidize easily - p-ethyl benzyl alcohol: has a benzylic primary alcohol (CH2OH), can be oxidized to an aldehyde Step 2 - Choose reagents that distinguish all three: Reagent 1: CrO3 (oxidizing agent) - p-ethyl benzyl alcohol (primary benzylic alcohol) is oxidized by CrO3 to give an aldehyde (benzaldehyde derivative) - p-ethyl phenol and p-methyl anisole do not undergo this oxidation under mild CrO3 conditions - This distinguishes p-ethyl benzyl alcohol from the other two Reagent 2: Tollen's reagent (ammoniacal AgNO3) - The aldehyde produced from p-ethyl benzyl alcohol after CrO3 oxidation gives a silver mirror test (positive) - Alternatively, the benzyl alcohol itself can be tested: Tollen's reagent oxidizes aldehydes, not alcohols directly, but in context, after CrO3 treatment the aldehyde gives a positive Tollen's test - This further confirms the presence of p-ethyl benzyl alcohol Reagent 3: FeCl3 - p-ethyl phenol gives a characteristic purple/violet color with FeCl3 (phenol test) - p-methyl anisole gives no color with FeCl3 (ether, no free OH) - This distinguishes p-ethyl phenol from p-methyl anisole Step 3 - Why other options fail: - Option (a) NaOH: Both phenol and benzyl alcohol react with Na (not NaOH selectively enough to differentiate all three cleanly); NaOH alone cannot oxidize benzyl alcohol to aldehyde for Tollen's test - Option (c) Tollen's reagent first: Tollen's reagent alone cannot oxidize a primary alcohol to aldehyde; without prior CrO3 oxidation, benzyl alcohol won't give silver mirror test directly - Option (d) Na: Na reacts with both phenol and benzyl alcohol (both have OH groups), so it cannot differentiate between them Step 4 - Option (b) CrO3, Tollen's reagent, FeCl3 provides a logical sequential differentiation: 1. CrO3 oxidizes benzyl alcohol to aldehyde (identifies p-ethyl benzyl alcohol) 2. Tollen's reagent confirms the aldehyde (silver mirror) 3. FeCl3 distinguishes p-ethyl phenol (positive violet color) from p-methyl anisole (no reaction) Therefore, the correct answer is B.