See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the reaction and substrate: The substrate is a tertiary alcohol (2,3-dimethyl-2-butanol or similar neopentyl-type tertiary alcohol based on the structure shown) treated with H3PO4 and heat. The products shown include two different alkenes, one of which appears to have a rearranged carbon skeleton (a geminal disubstituted alkene). Step 2 - Evaluate statement (1) Dehydration: H3PO4 with heat is a classic acid-catalyzed dehydration of an alcohol. Water is eliminated to form alkenes. Statement (1) is TRUE. Step 3 - Evaluate statement (2) E2 mechanism: Acid-catalyzed dehydration of alcohols proceeds via an E1 mechanism (not E2), because the OH is first protonated to form a good leaving group (water), generating a carbocation intermediate, which then loses a proton. E2 is a concerted bimolecular elimination requiring a strong base. H3PO4 is not a strong base, and tertiary carbocations favor E1. Statement (2) is FALSE. Step 4 - Evaluate statement (3) Carbon skeleton migration: The two products shown include one alkene whose structure suggests a rearranged carbon skeleton (hydride or methyl shift from the carbocation intermediate). The appearance of a rearranged product (with a different carbon skeleton, e.g., a neopentyl-type rearrangement) confirms that a 1,2-shift (carbon skeleton migration) has occurred. Statement (3) is TRUE. Step 5 - Evaluate statement (4) Most stable alkene will form: Under E1 conditions with acid and heat, Zaitsev's rule applies — the more substituted (more stable) alkene is the major product. The reaction conditions favor formation of the most stable alkene. Statement (4) is TRUE. Step 6 - Evaluate statement (5) Single-step reaction: E1 is a multi-step mechanism (protonation of OH, loss of water to form carbocation, loss of proton). It is not a single-step reaction. Statement (5) is FALSE. Step 7 - Select the correct combination: True statements: 1, 3, 4 → option (d). Therefore, the correct answer is D.