Describe the addition reactions of benzene with chemical equations.

(N/A) Benzene possesses unique stability; however,under vigorous conditions,benzene undergoes addition reactions. In these reactions,$3$ molecules of the reactant react with $1$ mole of benzene,which reflects the presence of three double bonds $(\pi)$ in the benzene structure.
$(i)$ Hydrogenation of benzene: Under vigorous conditions,i.e.,at high temperature and/or pressure in the presence of a nickel catalyst,the hydrogenation of benzene yields cyclohexane.
$C_{6}H_{6} + 3H_{2} \xrightarrow{Ni, \Delta, \text{Pressure}} C_{6}H_{12} \text{ (Cyclohexane)}$
$(ii)$ Chlorination of benzene: Under ultra-violet light,three chlorine molecules add to benzene to produce benzene hexachloride,$C_{6}H_{6}Cl_{6}$,which is also known as gammaxane or $BHC$.
$C_{6}H_{6} + 3Cl_{2} \xrightarrow{uv, 500 \ K} C_{6}H_{6}Cl_{6} \text{ (BHC/Gammaxane)}$
Note: Initially,Gammaxane was used as a domestic insecticide,but it is now banned.