Question

The addition of HBr to an alkene in the presence of peroxide is an example of :

• A. nucleophilic addition reaction
• B. electrophilic substitution reaction
• C. free radical addition reaction
• D. acid catalysed reaction

Answer 1

The correct option is C free radical addition reaction

In the presence of peroxide, addition of $HBr$ to unsymmetrical alkenes takes place contrary to Markovnikov’s rule. It is also known as peroxide or Kharasch effect. Peroxides such as $(PhCO{)}_2{O}_2$ can be considered for the reaction.

Addition reaction of $HBr$ to an unsymmetrical alkene in the presence of peroxide follows the free-radical mechanism. Here, bromine radical is formed which reacts with an alkene and produces an anti-markovnikov product.