Organic ChemistryHigh Yield (2-3 Qs in JEE)

Amines & Diazonium Salts Formulas

Basicity of amines in gas/aqueous phase, Hoffmann bromamide degradation, Gabriel phthalimide synthesis, and Sandmeyer reaction.

7 Formulas•585+ Questions in Bank

Core Formulas & Mathematical Identities

\text{R-CONH}_2 + \text{Br}_2 + 4\text{NaOH} \longrightarrow \text{R-NH}_2 + \text{Na}_2\text{CO}_3 + 2\text{NaBr} + 2\text{H}_2\text{O}

Step-down conversion of primary amide to primary amine with ONE LESS carbon atom.

Examiner Tip: Intermediate is isocyanate (R-N=C=O).

(\text{CH}_3)_2\text{NH} > \text{CH}_3\text{NH}_2 > (\text{CH}_3)_3\text{N} > \text{NH}_3 \quad (2^\circ > 1^\circ > 3^\circ > \text{NH}_3)

Combined result of inductive (+I), steric hindrance, and hydration stabilization.

Examiner Tip: In gaseous phase with no hydration: 3° > 2° > 1° > NH₃.

\text{Ar-NH}_2 \xrightarrow{\text{NaNO}_2 + \text{HCl, } 0-5^\circ\text{C}} \text{Ar-N}_2^+ \text{Cl}^- \xrightarrow{\text{Cu}_2\text{X}_2} \text{Ar-X} + \text{N}_2 \uparrow

Conversion of primary aromatic amine into benzene diazonium chloride and aryl halides.

Examiner Tip: Temperature must be strictly between 0°C and 5°C to prevent decomposition of diazonium salt.

\text{R-NH}_2 + \text{CHCl}_3 + 3\text{KOH} \xrightarrow{\Delta} \text{R-NC} \; (\text{Foul smell}) + 3\text{KCl} + 3\text{H}_2\text{O}

Specific test given ONLY by primary (1°) aliphatic and aromatic amines.

Examiner Tip: Secondary and tertiary amines do NOT give carbylamine test.

\text{Phthalimide} \xrightarrow{\text{KOH}} \text{K-Phthalimide} \xrightarrow{\text{R-X}} N\text{-alkyl phthalimide} \xrightarrow{\text{NaOH (aq)}} \text{R-NH}_2 \; (1^\circ \text{ Aliphatic Amine})

Clean synthetic preparation of pure 1° aliphatic amines free from 2° and 3° amine impurities.

Examiner Tip: Aromatic 1° amines (like Aniline) CANNOT be prepared by this method because aryl halides do not undergo SN2 displacement.

1^\circ: \text{Soluble in KOH}; \quad 2^\circ: \text{Insoluble in KOH}; \quad 3^\circ: \text{Does not react with } \text{PhSO}_2\text{Cl}

Benzene sulfonyl chloride (Hinsberg reagent) distinction between 1°, 2°, and 3° amines based on active hydrogen.

Examiner Tip: The sulfonamide from 1° amine contains an acidic N-H proton which dissolves in alkaline KOH.

\text{Ph-N}_2^+ \text{Cl}^- + \text{Ph-OH} \xrightarrow{pH \; 9-10} p\text{-Hydroxyazobenzene (Orange Dye)}, \quad \text{Ph-N}_2^+ \text{Cl}^- + \text{Ph-NH}_2 \xrightarrow{pH \; 4-5} p\text{-Aminoazobenzene (Yellow Dye)}

Electrophilic aromatic substitution of diazonium ion on highly activated aromatic rings.

Examiner Tip: Coupling with phenol requires mildly basic pH (9-10) to form phenoxide; coupling with aniline requires mildly acidic pH (4-5).

Frequently tested misconceptions in Amines & Diazonium Salts

•Basicity order of aliphatic amines in aqueous solution: for methyl group 2° > 1° > 3° > NH₃; for ethyl group 2° > 3° > 1° > NH₃.
•Aniline does NOT undergo Friedel-Crafts reaction because AlCl₃ forms a complex with the -NH₂ group.