Question

Explain the relative rate of $E2$ reaction of the given compounds.

• A. $III<I<II$
• B. $I<II<III$
• C. $III<II<I$
• D. None of these

Answer 1

The correct option is C $III<II<I$

The relative rate of $E_2$ reaction of the given compounds is $III<II<I$.

In the elimination reaction, a molecule of $HCl$ is eliminated. Elimination will be fastest when $H$ atom and $Cl$ atom are trans to each other. In compound $I$, both $H$ atoms are trans to $Cl$. Hence, the rate of elimination for compound $I$ is maximum.

In compound $III$, both $H$ atoms are cis to $Cl$. Hence, the rate of elimination for compound $III$ is minimum.

In compound $II$, only one $H$ atom is trans to $Cl$. Hence, the rate of elimination for compound $II$ is intermediate.

Hence option C is correct