Lewis acids are electron deficient species. They are responsible for, inducing heterolytic fission in halogen molecule.

Role of Lewis acid is to produce an electrophile. The eletrophile produce will attack on electron rich benzene ring to produce aryl bromides and chlorides.

$$\begin{aligned} \mathrm{AlCl}_3+\mathrm{Cl}_2 & \longrightarrow\left[\mathrm{AlCl}_4\right]^{-}+\mathrm{Cl}^{+} \\ \mathrm{AlBr}_3+\mathrm{Br}_2 & \longrightarrow\left[\mathrm{AlBr}_4\right]^{-}+\mathrm{Br}^{+} \end{aligned}$$

This electrophile will further attack on benzene.

Partial double bond character of a bond increses the strength of the bond and hence, decreases the stability. Phenol will not react with a mixture of NaBr and $\mathrm{H}_2 \mathrm{SO}_4$ because it is resonance stabilised. Due to resonance, partial double bond character arises in $\mathrm{C}-\mathrm{O}$ bond of phenol and it becomes more stable than alcohol. $\left(\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{CH}_2 \mathrm{OH}\right)$.

Reaction $$2 \mathrm{NaBr}+3 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow 2 \mathrm{NaHSO}_4+\mathrm{SO}_2+\mathrm{Br}_2+2 \mathrm{H}_2 \mathrm{O}$$

$\mathrm{CH}_3 \mathrm{CHICH}_3$ is the major product of the reaction. The mechanism of the reaction is as follows

$$\mathrm{HI} \rightleftharpoons \mathrm{H}^{+}+\mathrm{I}^{-}$$

Haloalkanes are slightly soluble in water. For the solubility to haloalkane in water, energy is required to overcome the attractions between its own molecules and to break the bonds between water molecules.

Less energy is released when new attractions are set up between the haloalkanes and the water molecules as these are not as strong as the original hydrogen bonds in water.

Resonance in halobenzene

From the above resonating structure it is very clear that electron density is rich at ortho and para position. Therefore, it is ortho and para directing not meta directing.