"The presence of an electron-withdrawing group $\left( -NO_2 \right)$ at the ortho and para positions in haloarenes increases the reactivity of haloarenes towards nucleophilic substitution reactions." Prove this with an example.

(N/A) In haloarenes,the presence of an electron-withdrawing group like $-NO_2$ facilitates the nucleophilic substitution of the $-Cl$ atom by an $-OH$ group. The presence of $-NO_2$ groups at ortho and para positions stabilizes the carbanion intermediate through resonance,thereby increasing the reactivity towards $S_NAr$ reactions.
Example:
$1$. Chlorobenzene $(C_6H_5Cl)$ requires harsh conditions ($623 \ K$ and $300 \ atm$ pressure) for the substitution of $-Cl$ by $-OH$.
$2$. $p$-Nitrochlorobenzene $(p-NO_2C_6H_4Cl)$ requires milder conditions $(443 \ K)$ for the same substitution.
$3$. As the number of $-NO_2$ groups increases at ortho/para positions,the reaction conditions become even milder:
- With two $-NO_2$ groups ($2$,$4$-dinitrochlorobenzene),the reaction occurs at $368 \ K$.
- With three $-NO_2$ groups ($2$,$4$,$6$-trinitrochlorobenzene),the reaction occurs simply by warming with water.