Amines name reactions

Name reactions

Gabriel phthalimide synthesis

$\displaystyle \text{phthalimide} \xrightarrow[\text{then R-X, then NaOH}]{\text{KOH}} \text{R-NH}_2$

Gives only primary aliphatic amines.

Hoffmann bromamide degradation

$\displaystyle \text{RCONH}_2 + \text{Br}_2 + 4\text{NaOH} \rightarrow \text{RNH}_2 + \text{Na}_2\text{CO}_3 + 2\text{NaBr} + 2\text{H}_2\text{O}$

The amine has one carbon fewer.

Carbylamine reaction

$\displaystyle \text{RNH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\text{heat}} \text{RNC} + 3\text{KCl} + 3\text{H}_2\text{O}$

Foul smell. A test for primary amines.

Diazotisation

$\displaystyle \text{C}_6\text{H}_5\text{NH}_2 \xrightarrow[273\text{-}278\ \text{K}]{\text{NaNO}_2,\ \text{HCl}} \text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^-$

Coupling reaction

$\displaystyle \text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{C}_6\text{H}_5\text{OH} \xrightarrow{\text{OH}^-} \text{p-hydroxyazobenzene}$

Forms an orange dye.

Tests and trends

• Hinsberg's reagent separates amines: the primary product dissolves in alkali, the secondary doesn't, and tertiary amines don't react.
• In water, the usual basicity order is 2° > 3° > 1° for methyl amines, and it can differ for ethyl amines.
• Aromatic amines are weaker bases than aliphatic ones, because the lone pair is delocalised into the ring.
• Direct nitration of aniline gives a mix including meta product, so the −NH₂ group is first protected by acetylation.