Explain peroxide effect ?
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Peroxide effect: The change in regioselectivity of the addition of HBr to an alkene or alkyne in the presence of a peroxide. The regioselectivity for the addition reactions of other electrophilessuch as HCl and H3O+ are not altered in the presence of a peroxide....
In the absence of a peroxide, HBr adds to propene via an ionicmechanism (with a carbocation intermediate) to give 2-bromopropane. Markovnikov's Rule is obeyed....
In the presence of a peroxide such as HOOH, HBr adds to propene in an anti-Markovnikov sense and via a radicalmechanism, giving 1-bromopropane....
HOPE IT HELPS YOU...
Normally, when a molecule HX adds to a carbon-carbon double bond, the hydrogen becomes attached to the carbon with the more hydrogens on already. This is known as Markovnikov's Rule.
Because the HBr adds on the "wrong way around " in the presence of organic peroxides, this is often known as the peroxide effect or anti-Markovnikov addition.
In the absence of peroxides, hydrogen bromide adds to propene via an electrophilic addition mechanism. That gives the product predicted by Markovnikov's Rule.