Question

The Markownikoff's rule is best applicable to the reaction:

• A. ${\text{C}}_{\text{2}}{\text{H}}_{\text{4}}\text{+}\text{HCl}$
• B. ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{+}{\text{Br}}_{\text{2}}$
• C. ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{+}\text{HBr}$
• D. ${\text{C}}_{\text{3}}{\text{H}}_{\text{8}}\text{+}{\text{Cl}}_{\text{2}}$

Answer 1

Answer: (C)

The Markownikoff's rule is best applicable to the reaction ${\text{C}}_{\text{3}}{\text{H}}_{\text{6}}\text{+}\text{HBr}$ i.e. unsymmetrical alkene with $\text{HBr}\text{.}$ This rule is used as a guidance for electrophilic addition in those cases where an asymmetrical reagent is added to an asymmetrical alkene, where the negative part of reagent attaches itself to that carbon atom that contains lesser number of hydrogen atoms.

In options $\text{(B)}$ and $\text{(D)}$ , reagent used is ${\text{Br}}_{\text{2}}$ and ${\text{Cl}}_{\text{2}}$ that gives addition reaction via free radial substitution. In option $\text{(A)}$ , alkene used is symmetrical. Hence, Markownikoff's rule is not applicable there.