Preparation Reactions

Nitro Reduction: $\text{RNO}_2 \xrightarrow{\text{Sn/HCl or H}_2\text{/Pd}} \text{RNH}_2$

Gabriel Phthalimide Synthesis: $\text{Phthalimide} \xrightarrow{\text{KOH}} \text{K-Phthalimide} \xrightarrow{\text{RX (SN2)}} \text{N-Alkylphthalimide} \xrightarrow{\text{N}_2\text{H}_4} \text{RNH}_2 \text{ (1° only)}$

Hoffmann Bromamide Degradation: $\text{RCONH}_2 + \text{Br}_2 + 4\text{NaOH} \rightarrow \text{RNH}_2 + \text{Na}_2\text{CO}_3 + 2\text{NaBr} + 2\text{H}_2\text{O}$ (Product amine has one fewer carbon than the amide)

Distinction Tests

Carbylamine Test (1° amines only): $\text{RNH}_2 + \text{CHCl}_3 + 3\text{KOH} \rightarrow \text{R-NC} (\text{isocyanide, foul smell}) + 3\text{KCl} + 3\text{H}_2\text{O}$

Hinsberg Test: 1° amine + $C_{6}H_{5}SO_{2}Cl$ → sulfonamide (N–H present) → soluble in NaOH 2° amine + $C_{6}H_{5}SO_{2}Cl$ → sulfonamide (no N–H) → insoluble in NaOH 3° amine + $C_{6}H_{5}SO_{2}Cl$ → no reaction

Diazonium Salt Reactions

Diazotization: $\text{ArNH}_2 + \text{NaNO}_2 + 2\text{HCl} \xrightarrow{0\text{–}5°C} \text{ArN}_2^+\text{Cl}^- + \text{NaCl} + 2\text{H}_2\text{O}$

Sandmeyer: $\text{ArN}_2^+ + \text{CuCl/HCl} \rightarrow \text{ArCl}; \quad \text{ArN}_2^+ + \text{CuBr/HBr} \rightarrow \text{ArBr}; \quad \text{ArN}_2^+ + \text{CuCN/KCN} \rightarrow \text{ArCN}$

Gattermann: $\text{ArN}_2^+ + \text{Cu (powder)/HCl} \rightarrow \text{ArCl}$

Schiemann (Balz-Schiemann): $\text{ArN}_2^+\text{Cl}^- + \text{HBF}_4 \rightarrow \text{ArN}_2^+\text{BF}_4^- \xrightarrow{\Delta} \text{ArF} + \text{BF}_3 + \text{N}_2$

Azo Coupling (with phenol): $\text{ArN}_2^+ + \text{C}_6\text{H}_5\text{OH} \xrightarrow{\text{alkaline}} \text{p-hydroxyazobenzene (orange-red)}$

Azo Coupling (with aniline): $\text{ArN}_2^+ + \text{C}_6\text{H}_5\text{NH}_2 \xrightarrow{\text{weakly acidic}} \text{p-aminoazobenzene (yellow)}$

Basicity (pKb values, approximate)

$\text{(CH}_3\text{)}_2\text{NH}: pK_b \approx 3.27 > \text{CH}_3\text{NH}_2: pK_b \approx 3.38 > \text{(CH}_3\text{)}_3\text{N}: pK_b \approx 4.19 > \text{NH}_3: pK_b \approx 4.74 \gg \text{C}_6\text{H}_5\text{NH}_2: pK_b \approx 9.38$