⚗️ Amines
1°=one R, 2°=two R, 3°=three R on nitrogen
Classifying Amines
Primary amine: one R group on N (RNH2). Secondary: two R groups (R2NH). Tertiary: three R groups (R3N). Quaternary ammonium: four R groups on N+ (R4N+) — positively charged, not a base.
⚗️ Amines
Basicity: alkyl amines > NH3 > aryl amines
Amine Basicity Order
Alkyl amines are stronger bases than ammonia (alkyl groups donate electrons). Aryl amines (aniline) are much weaker bases — lone pair delocalized into ring. EWG on ring further decrease basicity.
⚗️ Amines
Amines are nucleophiles — react with acid chlorides, esters, alkyl halides
Amine as Nucleophile
The nitrogen lone pair makes amines good nucleophiles. React with: acid chlorides → amides (fast). Esters → amides (slower). Alkyl halides → alkylation (gives higher substituted amine).
⚗️ Amines
Gabriel synthesis: phthalimide → primary amine only
Gabriel Synthesis
Only reliable way to make pure primary amines without over-alkylation. Phthalimide (N-H, pKa ~9) + base → anion → alkylate → hydrazine hydrolysis → primary amine + phthalhydrazide.
⚗️ Amines
Hofmann elimination: quaternary ammonium + heat → least substituted alkene
Hofmann Elimination
Opposite of Zaitsev — gives least substituted alkene (anti-Zaitsev). Bulky base attacks least hindered beta-H. Used to determine amine structure by identifying the alkene product.