What is the major product of the addition of HBr to 2-methylpropene in the presence of peroxides?
Correct: A
In the presence of peroxides, the addition of HBr to an alkene follows an anti-Markovnikov rule via a radical mechanism. This means the bromine atom will add to the carbon with more hydrogens. 2-methylpropene is (CH₃)₂C=CH₂. The carbon with the most hydrogens is the CH₂ group, so the bromine will add to this carbon. This yields 1-bromo-2-methylpropane.