Q.Account for the following:
i. Aniline does not undergo Friedel-Crafts reaction.
ii. Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
iii. pKb of aniline is more than that of methylamine.
iv. Gabriel phthalimide synthesis is preferred for synthesising primary amines.

Step 1. i. Aniline does not undergo Friedel-Crafts reaction: aniline is basic, and its nitrogen lone pair donates directly to the AlCl3 catalyst, forming a stable acid-base adduct (C6H5-NH2->AlCl3). This ties up the very Lewis acid the reaction needs to generate an electrophile, and it also removes the lone pair's activating resonance donation into the ring, so the reaction simply cannot proceed.

Step 2. ii. Diazonium salts of aromatic amines are more stable than aliphatic ones: an ARENEdiazonium cation's positive charge is delocalised over the ring through resonance (the terminal nitrogen's + charge shifts onto the ortho/para ring carbons), spreading and stabilising the charge. An aliphatic diazonium ion has no such adjacent pi system to delocalise into, so it decomposes essentially instantly, while the aromatic version survives briefly at low temperature.

Step 3. iii. pKb of aniline exceeds that of methylamine: aniline's nitrogen lone pair is drawn into conjugation with the ring (the same resonance effect from part ii), making it markedly LESS available for accepting a proton than an alkylamine's lone pair, which instead benefits from the alkyl group's electron-DONATING (+I) effect with no competing delocalisation. Less available lone pair means weaker base means HIGHER pKb. …

For each reasoning question, identify the single electronic or mechanistic cause (lone-pair/AlCl3 complexation; resonance delocalisation of a cation or lone pair into the ring; the phthalimide route's built-in one- …

• For part iii, explaining aniline's lower basicity purely by 'the ring pulls electrons away inductively' -- the dominant effect is specifically RESONANCE delocalisation of the lone pair INTO the ring (removing it from availability for pr …