Chemistry - Aromatic Hydrocarbon Question with Solution | TestHub

A-r; B-p, q; C- p, q, r; D-p Sodium fusion extract gives Prussian blue when nitrogen is present alongwith carbon. Phenolic group and carboxylate gives positive ${\mathrm{FeCl}}_3$ test - white precipitate comes with $\mathrm{AgCl}$. $$\text{ Hydrazone formation occurs effectively at }\mathrm{pH}\approx 4.5\text{. The reaction proceeds in that }$$ condition only when ${\mathrm{H}}^{+}$concentration is merely sufficient to activate. As ${\mathrm{H}}^{+}$concentration raises, sufficient molecule of hydrazone gets converted into hydrazonium which is not nucleophilic and reaction becomes impossible. Further, low concentration of ${\mathrm{H}}^{+}$(in the case of hydrolysis of 2, 4-dinitrophenyl hydrazonium bromide) is not effective to proceed elimination (rate determining step).
If it is assumed that the given hydrazonian bromiate is the result as salt main $\mathrm{HBr}$ is used as acid catalyst. Remember! hydrazone formation involves first addition and then elimination (res). In the second step substitution dominates over elimination ( $\mathrm{HBr}$ is not a dehydrating reagent mutually).