The increasing order of the following compounds for electrophilic substitution reaction is:
$(I)$ Toluene
$(II)$ Benzene
$(III)$ Benzoic acid

What is the role of $HNO_3$ in the nitrating mixture used for the nitration of benzene?

Find the products $(C)$ and $(E)$ in the following reaction sequences:
$n$-propyl bromide $\xrightarrow{Na} (A)$ $\xrightarrow[Al_2O_3/773 \ K]{CrO_3} (B)$ $\xrightarrow[500 \ K]{Cl_2/UV} (C)$
$n$-propyl bromide $\xrightarrow{Na} (A)$ $\xrightarrow[Al_2O_3/773 \ K]{CrO_3} (B)$ $\xrightarrow{CH_3Cl/AlCl_3} (D)$ $\xrightarrow{Cl_2/hv} (E)$

Which of the following compounds does not undergo the Friedel-Crafts reaction?

Benzene is relatively unreactive towards electrophilic addition reactions because

In the presence of sunlight,benzene reacts with $Cl_{2}$ to give product $X$. The number of hydrogens in $X$ is $.....$