See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Under acid-catalyzed conditions with heat, the reaction of ethylene (H2C=CH2) with isobutylene ((CH3)2C=CH2) proceeds via carbocation intermediacy and follows Markovnikov addition and rearrangement principles. Step 1: Identify the reactants. - Reactant 1: ethylene, H2C=CH2 - Reactant 2: isobutylene, (CH3)2C=CH2 Step 2: Under H+ (acid) catalysis, a proton adds to isobutylene following Markovnikov's rule, generating the more stable tertiary carbocation: (CH3)3C+ (tert-butyl cation). Step 3: The tertiary carbocation (CH3)3C+ can react with ethylene. The pi electrons of ethylene attack the carbocation, forming a new C-C bond and generating a primary carbocation: (CH3)3C-CH2-CH2+. Step 4: The primary carbocation (CH3)3C-CH2-CH2+ is unstable. It undergoes a 1,2-hydride shift to give a more stable secondary carbocation: (CH3)3C-CH+(CH2...) — actually, let us reconsider. The primary cation (CH3)3C-CH2-CH2+ undergoes 1,2-hydride shift: H migrates from adjacent carbon to give (CH3)3C-CH(+)-CH3, a secondary carbocation, or alternatively a 1,2-methyl/hydride shift. Step 5: More carefully: (CH3)3C-CH2-CH2+ → 1,2-H shift → (CH3)3C-CH+-CH3 (secondary carbocation) → further 1,2-H shift or methyl shift → (CH3)2C+-CH(CH3)2... Actually, reconsidering the product (c): option (c) appears to be 2-methylbut-2-ene, i.e., (CH3)2C=CHCH3, which is a trisubstituted alkene — the most stable alkene (Zaitsev product). Step 6: The sequence is: H+ adds to isobutylene → (CH3)3C+ (tertiary carbocation) → adds to ethylene → new primary carbocation (CH3)3C-CH2-CH2+ → 1,2-H shift → secondary carbocation (CH3)2C(CH3)-... leading ultimately to elimination giving the most stable (most substituted) internal alkene. The most thermodynamically stable product from C6 combination would be 2-methylbut-2-ene (from C5 framework) if we consider that the tert-butyl cation adds to ethylene to give a C6 cation, but the structure in option (c) suggests a C5 trisubstituted alkene consistent with 2-methylbut-2-ene: CH3-C(CH3)=CH-CH3. Option (a) fails - cyclobutane ring formation is not favored here. Option (b) fails - less substituted alkene, not the major product. Option (d) fails - terminal alkene, less stable than internal trisubstituted alkene. Option (c) is the most substituted, most stable alkene formed via carbocation rearrangement and elimination under thermodynamic control (heat). Therefore, the correct answer is C.