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Explain breifly about markownikoff's rule and kharasch effect.Give its applications.

Markovnikov's rule:

According to Markovnikov's rule, when an alkyl halide is added to an alkene, then the hydrogen from alkyl halide attaches to the carbon atoms with lesser number of alkyl substituents. And the halide group attaches to the carbon with more number of alkyl substituents.

Example: 

 

Kharasch Effect:

 

According to Kharasch effect, in presence of peroxide, the reaction of an alkyl halide with an alkene does not proceed in accordance with Markovnikov's rule. This effect is limited to only HBr. 

 

Here, hydrogen from HBr attaches to the carbon atom with more number of alkyl substituents and the halide group attaches to the carbon atom with lesser number of alkyl substituents.

Example: 

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The Markovnikov's rule states that when to an unsymmetrical alkene a reagent is added then the negative part of the addendum (adding molecule) gets attached to that carbon atom which possesses lesser number of hydrogen atoms. For example

 

The anti- Markovnikov's rule is the reverse of the above and states that when to an unsymmetrical alkene a reagent is added then the negative part of the addendum (adding molecule) gets attached to that carbon atom which possesses more number of hydrogen atoms. It is normally followed when hydrogen and many other peroxide is added to a reaction system. Thus when the reaction system contains peroxides, anti- Markovnikov's rule will be followed. If any particular reagent has not been mentioned, then Markovnikov's rule will be followed. Example, in the following reaction anti-Markovnikov's rule is followed due to the presence of peroxide

 

 

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