Chemistry - Halogen Derivative Question with Solution | TestHub

In (P), Br is replaced by CN → this is nucleophilic substitution via KCN, which gives R–CN (cyanide attached through carbon). Hence P → (2).

In (Q), alkene gives alcohol with anti-Markovnikov addition → this is hydroboration–oxidation (B₂H₆/THF, H₂O₂/OH⁻). So Q → (4).

In (R), Br is converted to NC (isocyanide) → AgCN gives R–NC due to covalent nature. Hence R → (3).

In (S), alkene forms alcohol via Markovnikov addition → oxymercuration–demercuration or acid hydration. So S → (1), (5).

KCN → C-attack (cyanide), AgCN → N-attack (isocyanide) is key concept.

Hydroboration gives anti-Markovnikov alcohol, while Hg(OAc)₂/H₂O gives Markovnikov alcohol.