Question

Deviation from Markownikoff's rule occurs in presence of
A) Zinc
B) Peroxides
C) \[Hg-Zn/HCl\]
D) All of these

Answer 1

Hint: The electrophilic addition of hydrogen halide to alkene according to Markownikoff’s rule. Deviation from this rule takes place if the reaction proceeds through a different mechanism. This different mechanism is generally followed by the alkene in the presence of any free radical producing compound.

Complete Step by Step Answer:
In electrophilic addition reaction hydrogen halide gets attached to the alkene. In this reaction in the first step the alkene gets protonated to give the stable carbocation. In the next step, a nucleophile that is a halide atom attacks the carbocation to form the desired alkyl halide.

Electrophilic addition on a carbon-carbon double bond involves the intermediate formation of a more stable carbocation. This statement is called Markownikoff's rule.

According to the markownikoff’s rule of electrophilic addition in carbon-carbon double bond the carbocation which contains the more substituent is the most stable one and halide attacks that carbon atom of alkene.

In electrophilic addition reaction when the alkene is treated with alkyl halide in presence of peroxide then the least stable carbocation forms the major product. This rule is called anti markovnikov's rule. This reaction proceeds through a free radical mechanism. Thus deviation from Markownikoff's rule occurs in presence of Peroxides.
Thus the correct option is B.

Note: Peroxide contains oxygen oxygen linkage commonly called as peroxo linkage. In presence of heat or light the peroxo linkage breaks down to form free radicals. Free radical is an initiator in any reaction.