See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The compound is CH3CH2C(OH)(CH3)CH(CH3)2, which is 3-methyl-3-pentanol... Let me re-read: CH3-CH2-C(OH)(CH3)-CH(CH3)2. The carbon bearing OH (call it C1 of the dehydration) has: CH3, CH2CH3, OH, and CH(CH3)2 attached. This is a tertiary alcohol. Step 2 - Acid-catalyzed dehydration mechanism: Under H+/heat, the tertiary alcohol undergoes E1 elimination. Protonation of OH gives water as a leaving group, forming a tertiary carbocation at the carbon that bore the OH: [CH3CH2-C+(CH3)-CH(CH3)2]. Step 3 - Carbocation stability and rearrangement: The tertiary carbocation formed is CH3CH2-C+(CH3)-CH(CH3)2. Check if a 1,2-hydride or methyl shift gives a more stable carbocation. The adjacent carbon CH(CH3)2 has an H that could shift. A 1,2-hydride shift from CH(CH3)2 to the carbocation center would give: CH3CH2-CH(CH3)-C+(CH3)2. This new carbocation is also tertiary (three methyl/alkyl groups). Actually the original carbocation is tertiary (CH2CH3, CH3, CH(CH3)2 = three carbon groups). The rearranged carbocation CH3CH2CH(CH3)C+(CH3)2 is also tertiary. However, rearrangement is favorable because the rearranged cation leads to a more substituted alkene. Step 4 - Elimination from rearranged carbocation: From the rearranged carbocation CH3CH2-CH(CH3)-C+(CH3)2, loss of a proton gives the most substituted (Zaitsev) alkene. Loss of H from CH(CH3) gives: CH3CH2-C(CH3)=C(CH3)2, which is (CH3CH2)(CH3)C=C(CH3)2 — a trisubstituted alkene. This corresponds to option (d): left C has CH3 and CH2CH3, right C has CH3 and CH3. Step 5 - Why other options fail: (a) and (b) represent alkenes from elimination of the original carbocation without rearrangement, giving less substituted products. (c) represents a terminal alkene (=CH2), which would be the least substituted and least favored product. (d) (CH3CH2)(CH3)C=C(CH3)2 is the most substituted alkene possible after the 1,2-hydride shift rearrangement, consistent with Zaitsev's rule, making it the major product. Therefore, the correct answer is D.