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2 -Methylpentan- 3 -ol is heated with concentrated H₂SO₄ to yield a major alkene B . Alkene B is then treated with HBr in the presence of peroxide to form product C . The total number of possible stereoisomers for product C is ________.

Correct answer

2

Step-by-step solution

Protonation of 2 -methylpentan- 3 -ol followed by the loss of a water molecule forms a secondary carbocation at C3 : CH₃-CH(CH₃)-CH⁺-CH₂-CH₃ . A 1,2 -hydride shift occurs from C2 to C3 to form a more stable tertiary carbocation: CH₃-C⁺(CH₃)-CH₂-CH₂-CH₃ . Elimination of a proton from the adjacent carbon yields the more substituted, major Saytzeff alkene B , which is 2 -methylpent- 2 -ene: CH₃-C(CH₃)=CH-CH₂-CH₃ . Reaction of alkene B with HBr in the presence of peroxide follows anti-Markovnikov regioselectivity. The

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