In case of alkyl aryl ethers, the products are always phenol and an alkyl halide because due to resonance $\mathrm{C}_6 \mathrm{H}_5-\mathrm{O}$ bond has partial double bond character. The mechanism is given below

Mechanism Protonation of anisole gives methylphenyl oxonium ion.

In this ion, the bond between $\mathrm{O}-\mathrm{CH}_3$ is weaker than the bond between $\mathrm{O}-\mathrm{C}_6 \mathrm{H}_5$ which has partial double bond character. This partial double bond character is due to the resonance between the lone pair of electrons on the O -atom and the $s p^2$ hybridised carbon atom of the phenyl group. Therefore, attack by $I^{-}$ion exclusively breaks the weaker $\mathrm{O}-\mathrm{CH}_3$ bond forming methyl iodide and phenol.

(a) The starting material used in the industrial preparation of phenol is cumene.

(b) Phenols when treated with bromine water gives polyhalogen derivatives in which all the hydrogen atoms present at ortho and para positions with respect to - OH group are replaced by bromine atoms.

However, in non-aqueous medium such as $\mathrm{CS}_2, \mathrm{CCl}_4, \mathrm{CHCl}_3$, monobromophenols are obtained.

In aqueous solution, phenol ionises to form phenoxide ion. This ion activates the benzene ring to a very large extent and hence the substitution of halogen takes place at all three positions.

On the other hand, in non-aqueous solution ionisation of phenol is greatly suppressed. Therefore, ring is activated slightly and hence monosubstitution occur.

(c) Lewis acid is an electron deficient molecule. In bromination of benzene, Lewis acid is used to polarise $\mathrm{Br}_2$ to form $\mathrm{Br}^{+}$electrophile.

In case of phenol, oxygen atom of phenol itself polarises the bromine molecule to form $\mathrm{Br}^{+}$ion (electrophile). So, Lewis acid is not required in the bromination of phenol.

Phenol is converted into salicylic acid. This salicylic acid is treated with acetic anhydride. On acetylation of salicylic acid, aspirin (acetyl salicylic acid) is formed.

Enzymes are biocatalyst. These biocatalysts (enzymes) are used in the industrial preparation of ethanol. Ethanol is prepared by the fermentation of molasses - a dark brown coloured syrup left after crystallisation of sugar which still contains about $40 \%$ of sugar.

The process of fermentation actually involves breaking down of large molecules into simple ones in the presence of enzymes. The source of these enzymes is yeast. The various reactions taking place during fermentation of carbohydrates are

$\underset{\text { Sucrose }}{\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}}+\mathrm{H}_2 \mathrm{O} \xrightarrow{\text { Invertase }} \underset{\text { Glucose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}+\underset{\text { Fructose }}{\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6}$

$$\mathrm{\mathop {{C_6}{H_{12}}{O_6}}\limits_{Glu\cos e} \buildrel {Zymase} \over \longrightarrow \mathop {2{C_2}{H_5}OH}\limits_{Ethyl\,alcohol} + 2C{O_2}}$$

In wine making, grapes are the source of sugars and yeast. As grapes ripen, the quantity of sugar increases and yeast grows on the outer skin. When grapes are crushed, sugar and the enzyme come in contact and fermentation starts. Fermentation takes place in anaerobic conditions i.e., in absence of air. $\mathrm{CO}_2$ gas is released during fermentation.

The action of zymase is inhibited once the percentage of alcohol formed exceeds 14 per cent. If air gets into fermentation mixture, the oxygen of air oxidises ethanol to ethanoic acid which in turn destroys the taste of alcoholic drinks.