(i) Gabriel's phthalimide synthesis: Phthalimide when treated with alcoholic potassium hydroxide is easily converted into potassium phthalimide which on treatment with alkyl halide followed by hydrolysis with acid or alkali yields phthalic acid and a primary amine.
(ii) Coupling reaction: It involves the reaction of benzene diazonium salts with phenols or aryl amines. Coupling of phenol takes place in mild alkaline solution while with aromatic 10 amines in mild, acidic medium.

Both aliphatic and aromatic nitro compounds on reduction in neutral medium, i.e., Zn dust and NH4Cl solution, give the corresponding hydroxylamines.
 \({ C }_{ 6 }{ H }_{ 5 }{ NO }_{ 2 }\quad \quad \overset { Zn/{ NH }_{ 4 }Cl,{ H }_{ 2 }O }{ \underset { \Delta }{ \longrightarrow } } \quad \quad { C }_{ 6 }{ H }_{ 5 }NHOH\\ Nitrobenzene\quad \quad \quad \quad \quad phenylhydroxylamine\\ \)
These hydroxylamines, when warmed with Tollens' reagent, are easily oxidized to the corresponding nitroso compounds and thus reduce Tollens' reagent to metallic silver
 \({ C }_{ 6 }{ H }_{ 5 }NHOH+2{ \left[ Ag{ \left( { NH }_{ 3 } \right) }_{ 2 } \right] }^{ + }+2{ OH }^{ - }\longrightarrow { C }_{ 6 }{ H }_{ 5 }N=O+2Ag\downarrow +4{ NH }_{ 3 }+2{ H }_{ 2 }O\)
This reaction is called Baker Mulliken's test and is used as a test for detection of nitro group in organic compounds.

Pyridine and other bases are used to remove the side product(HCI) from the reaction mixture.

It is because it will get oxidised with nitric acid if it is not acetylated.

HNO acts as a base in the nitrating mixture (conc.HNO₃+conc.H₂SO₄). H₂SO₄ acts on HNO₃ to generate the electrophile, \({ NO }_{ 2 }^{ + }\) (nitronium ion)

Four structural isomers are possible.