In the presence of peroxide, addition of HBr to propene takes place according to anti-Markovnikov's rule but peroxide effect is not seen in the case of HCl and HI. Explain.

In the presence of peroxide, addition of HBr to propene takes place ac

1.	In the presence of peroxide, addition of HBr to propene takes place according to anti-Markovnikov's rule but peroxide effect is not seen in the case of HCl and HI. Explain.
Answer» SOLUTION :In presence of peroxides, addition of HBr to propene takes place according to anti-markovnikov's rule. The reaction occurs by a FREE radical MECHANISM as shown below : In CASE of HBr both these steps are exothermic and hence peroxide effect is observed. However, in case of HCl or HI, EITHER first on the second step is endothermic and hence peroxide effect is not observed.