See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The compound is a cyclohexene diol with a tertiary alcohol bearing two methyl groups at C1 (gem-dimethyl), a double bond between C2 and C3, and a secondary hydroxyl at C6 (adjacent to C1). Step 2 - Reaction conditions: Acid (H+) and heat promote dehydration. With a diol on a cyclohexene ring under these conditions, the goal is aromatization (loss of water molecules to form a benzene ring). Step 3 - Mechanism toward aromatization: Under acidic conditions and heat, the diol undergoes acid-catalyzed dehydration. The tertiary OH at C1 is protonated and lost easily to form a tertiary carbocation. The secondary OH at C6 can also be lost. Multiple dehydrations and/or 1,2-shifts plus oxidation (loss of H2) or repeated eliminations drive the cyclohexadiene intermediate toward full aromatization. Step 4 - Counting carbons and methyl substituents: The ring has 6 carbons. C1 bears two methyl groups (gem-dimethyl) and C6 bears no extra substituents (just H). Upon aromatization, one of the gem-dimethyl groups at C1 must be lost (as water or via a 1,2-hydride/methyl shift) or one methyl migrates. Actually, on aromatization the ring carbon C1 can only bear one substituent on a benzene ring. The two methyls at C1: one stays on C1 as a ring substituent (methyl on the benzene ring), and the adjacent C6 (which had the OH) becomes another ring carbon. Step 5 - Determining substitution pattern: With the double bond already at C2-C3, upon full dehydration/aromatization the two methyl groups at C1 mean one methyl is on the ring carbon at position 1. The C6-OH elimination places the second point of unsaturation adjacent (C6-C1 bond area). The resulting aromatic compound has methyl groups at C1 and C2 positions of the benzene ring (the two methyls end up on adjacent carbons after the ring achieves full aromatization through the existing C2=C3 double bond and further dehydrogenation), giving 1,2-dimethylbenzene (o-xylene). Step 6 - Why not other options: (a) m-xylene would require methyls at 1,3 positions - not consistent with the gem-dimethyl at C1 and adjacent OH at C6. (c) Ethylbenzene would require a C2 side chain - no rearrangement of that type is favored. (d) p-xylene would require methyls at 1,4 positions - geometry doesn't match. The 1,2-relationship of the substituents (gem-dimethyl C1 and adjacent C6) leads directly to o-xylene upon aromatization. Therefore, the correct answer is B.