Question

sir what is markoffins rule and anti markoffins rule i dont understand

Answer 1

Markownikoff's and Anti-Markownikoff's rule help us to predict the product formed on addition of H-X (where x is usually Cl or Br) to alkene.

Markownikoff's rule follows "rich become rich, poor becomes poorer" analogy. It states that "on addition of H-X to alkene, the negative part of addendum (that is X¯ or Cl¯/Br¯) goes to the carbon which has less number of hydrogen attached to it.

Example :

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But hey!Don't be too much dependent on this rule, be careful, it's not applicable to all alkenes. Since it involves formation of carbocation, rearrangement may take place.

Example :

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So, before using this rule justcheck if 2° carbocation is rearrange-able (look if there is any adjacent tertiary carbon).

Anti-Markownikoff's rule is just the opposite, it follows " rich becomes poor, and poor becomes rich" analogy. It is applicable only when you perform the reaction in PRESENCE OF PEROXIDE and only when you add H-Br to alkene. In this case, the negative part of addendum goes to the carbon which has more number of carbon attached to it.

Example :

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Feel free to use this rule anywhere. Since it involves free radicals, rearrangement does not take place.
But, again be careful, it is only applicable to H-Br. Suppose if I were to take H-Cl in presence of peroxide, product will be formed according to Markownikoff's rule.