Alcohols undergo a number of reactions involving the cleavage of $\text{C} - \text{OH}$ bond. However, phenols do not undergo reactions involving the cleavage of $\text{C} - \text{OH}$ bond. Alcohols are weaker acids than water. Alcohols react with halogen acids to form the corresponding haloalkanes. Phenols are stronger acids than alcohols. A characteristic feature of phenols is that they undergo electrophilic substitution reactions such as halogenation, nitration, etc. Since $-\text{OH}$ group is a strong activating group, phenol gives trisubstituted products during halogenation, nitration, etc. (a) What happens when phenol is treated with the following ? (i) $\text{Br}_2$ water (ii) $\text{Conc. HNO}_3$ (b) (i) Write the mechanism of alcohol reacting as nucleophile in a reaction with $\text{CH}_3^{\oplus}$. OR (b) (ii) Why do phenols not undergo reactions involving cleavage of $\text{C} - \text{OH}$ bond ?