See image — Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: mCPBA is an epoxidation reagent that converts alkenes to epoxides. In the presence of H+, mCPBA still primarily acts as a peracid epoxidizing agent. The key question is which double bond gets epoxidized preferentially. Step 1: Identify the two double bonds in the starting material CH3-C(CH3)=C(CH3)-CH2-CH=CH2. - Double bond 1: The internal, trisubstituted (or tetrasubstituted) alkene: C(CH3)=C(CH3) — this is a more substituted (electron-rich) double bond. - Double bond 2: The terminal alkene CH=CH2 — this is a monosubstituted, less electron-rich double bond. Step 2: mCPBA preferentially epoxidizes the more electron-rich (more substituted) double bond. The internal double bond C(CH3)=C(CH3) is more substituted and more nucleophilic, so it reacts faster with the electrophilic peracid oxygen. Step 3: Epoxidation of the internal double bond gives an epoxide bridging those two carbons, leaving the terminal vinyl group (CH=CH2) intact. Step 4: This matches option (b): CH3-C(CH3)-C(CH3)-CH2-CH=CH2 with an epoxide (O bridge) between the two central carbons, and the terminal double bond remaining unreacted. Step 5: Why other options fail: - Option (a): Epoxidizes the terminal double bond (less substituted), which is not preferred. - Option (c): Shows a diol at the terminal end, which would result from osmylation or acid-catalyzed ring opening of terminal epoxide, not the major product here. - Option (d): Shows a diol at the internal positions, which would require ring opening of the internal epoxide; under the given conditions (just H+, not aqueous workup emphasized as ring-opening step), the epoxide itself is the major product. Therefore, the correct answer is B.