(a) Solution

(i) Zwitter ion structure for sulphanilic acid: [1 Mark]

Sulphanilic acid ($p\text{-aminobenzenesulphonic acid}$) exists as a zwitter ion due to the internal acid-base reaction between the basic $-\text{NH}_2$ group and the acidic $-\text{SO}_3\text{H}$ group.

(ii) Controlling the activating effect of $-\text{NH}_2$ group: [1 Mark]

The activating effect of the $-\text{NH}_2$ group is controlled by acetylation. By reacting aniline with acetic anhydride or acetyl chloride in the presence of pyridine, the $-\text{NH}_2$ group is converted into an acetanilide group ($-\text{NHCOCH}_3$).

Step-by-step logic:

• The lone pair of nitrogen in the acetanilide group participates in resonance with the carbonyl group ($>\text{C}=\text{O}$), reducing its electron-donating capacity to the benzene ring.
• This prevents poly-substitution and oxidation, allowing for controlled electrophilic substitution.

(b) Solution (OR Choice)

(i) Reaction of benzenediazonium chloride with ethanol: [1 Mark]

Step 1 (Reaction Equation): Benzenediazonium chloride is reduced by ethanol, which itself gets oxidized to acetaldehyde.

Step 2 (Final Product): The main organic product is Benzene.

(ii) Conversion: Bromoethane to Propanamine: [1 Mark]

Step 1 (Step-wise Working):

• Step A: React bromoethane with alcoholic $\text{KCN}$ to increase the carbon chain. $$ \text{CH}_3\text{CH}_2\text{Br} + \text{KCN (alc.)} \rightarrow \text{CH}_3\text{CH}_2\text{CN} + \text{KBr} $$
• Step B: Reduction of propanenitrile using $\text{LiAlH}_4$ or $\text{H}_2/\text{Ni}$. $$ \text{CH}_3\text{CH}_2\text{CN} + 4[\text{H}] \xrightarrow{\text{LiAlH}_4} \text{CH}_3\text{CH}_2\text{CH}_2\text{NH}_2 $$

Step 3 (Final Product): Propan-1-amine ($\text{CH}_3\text{CH}_2\text{CH}_2\text{NH}_2$).