Markovnikov's Rule in Alkene Addition

Steps:

• Structure of 2-methyl-2-butene is (CH3)2C=CHCH3, with unsymmetrical double bond.
• H+ from HBr adds to less substituted C3 (with more H's), forming tertiary carbocation at C2: (CH3)2C+-CH2CH3.
• Br- adds to tertiary carbocation at C2.
• Product is (CH3)2CBrCH2CH3, the major due to carbocation stability.

Why B is correct:

• B shows tertiary bromide at C2, consistent with Markovnikov's rule where H adds to carbon with more hydrogens, yielding most stable carbocation.

Why the others are wrong:

• A: Secondary bromide at C3, from anti-Markovnikov addition (minor without peroxides).
• C: Primary bromide, requires unlikely rearrangement to less stable carbocation.
• D: Secondary bromide identical to A, incorrect regiochemistry.

Final answer: B