See image — Alcohols Phenols and Ethers Chemistry Question

💡 Solution & Explanation

Concept: Acylation of hydroxyl groups. When a compound containing -OH groups undergoes acylation (e.g., with acetic anhydride or acetyl chloride), each -OH group is replaced by -OCOCH3 (acetyl group). Each acetylation replaces -H (mass = 1) with -COCH3 (mass = 43), giving a net mass increase of 42 per -OH group. Step 1: Calculate the increase in molar mass upon acylation. Molar mass of product = 390 Molar mass of compound (A) = 180 Increase in molar mass = 390 - 180 = 210 Step 2: Determine the number of -OH groups. Each -OH group that undergoes acylation increases the molar mass by 42 (since -H is replaced by -COCH3, i.e., +42 per group). Number of -OH groups = 210 / 42 = 5 Step 3: Verify with known compound. Glucose (C6H12O6) has molar mass = 180 and contains 5 -OH groups. Upon complete acetylation, each OH gains 42 mass units: 180 + 5(42) = 180 + 210 = 390. This matches perfectly. Why other options fail: - (b) 6: Would give mass increase of 252, product mass = 432, not 390. - (c) 10: Would give mass increase of 420, product mass = 600, not 390. - (d) 1: Would give mass increase of 42, product mass = 222, not 390. Therefore, the correct answer is A.