Describe the electrophilic aromatic substitution reactions of phenol.

(N/A) Phenol undergoes electrophilic aromatic substitution reactions due to the activating effect of the $-OH$ group,which directs incoming electrophiles to the ortho and para positions.
$1$. Nitration:
- With dilute $HNO_3$ at $298 \ K$,phenol gives a mixture of $o$-nitrophenol and $p$-nitrophenol.
- With concentrated $HNO_3$,phenol is converted into $2,4,6$-trinitrophenol,commonly known as picric acid.
$2$. Sulphonation:
- Phenol reacts with concentrated $H_2SO_4$ to form $o$-phenolsulphonic acid at low temperature $(293 \ K)$ and $p$-phenolsulphonic acid at higher temperature $(373 \ K)$.