Which of the following has the highest reactivity towards nucleophilic substitution reaction involving the cleavage of the $C-Cl$ bond?

Number of deactivating groups in the following is $-Cl, -SO_3H, -OH, -NHC_2H_5, -COOCH_3, -CH_3$.

Trichloroacetaldehyde,$CCl_3CHO$,reacts with chlorobenzene in the presence of sulphuric acid and produces:

Replacement of $Cl$ of chlorobenzene to give phenol requires drastic conditions,but chlorine of $2,4-$dinitrochlorobenzene is readily replaced because:

Which of the following groups is an ortho and para directing group?

Rank the following compounds in order of decreasing rate of reaction with alkoxide ion $(CH_3CH_2O^{-})$ in a nucleophilic aromatic substitution reaction:
$1$. $1$-bromo-$2$-nitrobenzene
$2$. $1$-bromo-$3$-nitrobenzene
$3$. $1$-bromo-$2,4$-dinitrobenzene
$4$. $1$-bromo-$3,4$-dinitrobenzene