Give the reaction for the formation of $m$-dinitrobenzene from benzene.

(N/A) The formation of $m$-dinitrobenzene from benzene involves two steps of electrophilic aromatic substitution (nitration):
$1$. First,benzene reacts with a mixture of concentrated $HNO_3$ and concentrated $H_2SO_4$ at $323-333 \ K$ to form nitrobenzene: $C_6H_6 + HNO_3 \xrightarrow{conc. H_2SO_4} C_6H_5NO_2 + H_2O$.
$2$. Second,nitrobenzene is further nitrated using fuming $HNO_3$ and concentrated $H_2SO_4$ at $373 \ K$. Since the $-NO_2$ group is meta-directing,the second nitro group enters the meta-position: $C_6H_5NO_2 + HNO_3 \xrightarrow{conc. H_2SO_4, 373 \ K} C_6H_4(NO_2)_2 + H_2O$.