User:Benjah-bmm27/degree/2/TJS

Introduction

"Aromatic Compounds and Amines", Professor Tom Simpson FRS

Amines

• CLW for amines
  • amine alkylation
  • Gabriel synthesis
  • sodium azide amine synthesis
  • reductive amination (with NaBH₃CN)
  • Hofmann rearrangement
  • nitrosation

Aromatic compounds

Electrophilic aromatic substitution

• Benzene does not easily undergo electrophilic addition, unlike alkenes...
• ...so it undergoes electrophilic aromatic substitution instead

Adding particular substituents

• Halo groups, -X: electrophilic halogenation
• Nitro groups, -NO₂: aromatic nitration
• Sulfo groups, -SO₂OH: aromatic sulfonation
• Organyl groups, -R:
  • Alkyl groups: Friedel-Crafts alkylation
  • Acyl groups: Friedel-Crafts acylation
  • Formyl group: Gattermann-Koch reaction
    • HCO⁺ is an intermediate

Substitution patterns

• Activating and deactivating groups, and the arene substitution patterns they cause
  • Inductive and mesomeric effects

Ipso substitution

• Ipso substitution
  • Grignard reaction with aryl halides
    • PhBr + Mg → PhMgBr
    • PhMgBr + E⁺ → PhE + [MgBr]⁺
    • if E = RCHO then PhE = PhCH(OH)R
    • if E = CO₂ then PhE = PhCO₂H
  • via aryldiazonium ions, [ArN₂]⁺
    • nitrosation of aryl amines at 0 °C with HNO₂:
      • HNO₂ formed in situ from NaNO₂ and HCl): NaNO₂ + HCl → HNO₂ + NaCl
      • ArNH₂ + HNO₂ → [ArN₂⁺][Cl⁻]
    • Sandmeyer reactions: PhN₂⁺ + CuX (and sometimes KX, too) → PhX + N₂
      • apparently go via a radical-nucleophilic mechanism involving an aryl radical
      • an easy route to PhI: PhN₂⁺ + CuI + KI → PhI + N₂
        • chemically feasible unlike the prohibitively expensive PhH + I₂ + AgNO₃ → PhI + AgI + HNO₃)
    • Balz–Schiemann reaction: an easy route to PhF
      • PhN₂⁺ + HBF₄ → PhF + N₂ + BF₃ + H⁺
      • mild conditions unlike the explosively exothermic PhH + F₂ + cat. AlF₃ → PhF + HF
    • Gomberg-Bachmann reaction: aryl-aryl coupling via ArH + Ar′N₂⁺ + base → Ar-Ar′

Nucleophilic aromatic substitution

• Nucleophilic aromatic substitution

Functional group interconversions in aromatics

• Wolff-Kishner reduction (KOH, N₂H₄)
• Clemmensen reduction (Zn, HCl)
• Reduction of nitro compounds
  • e.g. with SnCl₂ in HCl
• Baeyer-Villiger oxidation

Later topics

• Electrophilic aromatic substitution of naphthalene
• Birch reduction
• Claisen rearrangement
• Fries rearrangement