See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: When an alcohol reacts with acetic anhydride (Ac2O), each -OH group undergoes acetylation. The -OH is replaced by -OCOCH3 (acetate group), and acetic acid (CH3COOH) is released as a byproduct. Reaction per -OH group: -OH + (CH3CO)2O --> -OCOCH3 + CH3COOH Net change per -OH group: The -OH (formula contribution: H) is replaced by -OCOCH3 (formula contribution: COCH3 = C2H3O). So the net gain per -OH group is: add C2H2O (since we replace H with C2H3O, net addition = C2H3O - H = C2H2O). Wait, let me be more precise. Starting fragment: -OH. After acetylation: -O-CO-CH3. Change: -OH becomes -O-CO-CH3 Difference: remove H, add CO-CH3 = add C2H3O Net addition per OH group = C2H3O - H = C2H2O For 3 OH groups: net addition = 3 × C2H2O = C6H6O3 Verification: Glycerol is C3H8O3. Triacetin (glycerol triacetate) is C9H14O6. Difference: C9H14O6 - C3H8O3 = C6H6O3. This confirms the answer. Why other options fail: (a) C4H4O2 - incorrect count, not consistent with 3 acetylations (b) C6H6O6 - overestimates oxygen; each acetylation adds only one extra O (the carbonyl O), not two (c) C6H6O2 - underestimates oxygen (d) C6H6O3 - correct, matches the calculated difference Therefore, the correct answer is D.