Amines are classified as primary ($RNH_{2}$), secondary ($R_{2}NH$), or tertiary ($R_{3}N$) based on the number of carbon substituents on the nitrogen atom.

Gabriel phthalimide synthesis is selective for primary aliphatic amines only; it cannot produce aromatic amines ($ArNH_{2}$) because aryl halides do not undergo SN2 reactions.

Hoffmann bromamide degradation converts an amide ($RCONH_{2}$) into a primary amine ($RNH_{2}$) with one fewer carbon atom, as the carbonyl carbon is lost as $Na_{2}CO_{3}$.

In aqueous solution, the basicity order of aliphatic amines is 2° > 1° > 3° > $NH_{3}$, because the conjugate acid of a tertiary amine ($R_{3}NH^{+}$) is poorly solvated by water due to steric bulk.

Aniline is a much weaker base than any aliphatic amine (pKb ≈ 9.38) because its lone pair is delocalized into the benzene ring by resonance, reducing its availability for protonation.

The carbylamine test ($CHCl_{3}$ + KOH → foul isocyanide RNC) is specific only to primary amines; secondary and tertiary amines give no reaction.

The Hinsberg test uses benzenesulfonyl chloride with NaOH: the 1° sulfonamide dissolves in NaOH (has N–H), the 2° sulfonamide is insoluble (no N–H), and the 3° amine does not react at all.

Diazotization of aromatic primary amines requires strict 0–5 °C conditions ($NaNO_{2}$ + 2HCl) because diazonium salts decompose above 5 °C.

The Schiemann (Balz-Schiemann) reaction ($ArN_{2}^{+}$ + $HBF_{4}$ → ArN_{2}^{+}$$BF_{4}^{-} →$\Delta$ ArF + $BF_{3}$ + $N_{2}$) is the only reliable method to introduce fluorine onto an aromatic ring.

Azo coupling of diazonium salts with phenol requires alkaline medium (to form reactive phenoxide), while coupling with aniline requires weakly acidic medium (to keep –$NH_{2}$ free and reactive).