Organic chemistry - Chapter 8: Arenes - Nam Phan

CRITERIA FOR AROMATICITY
To be classified as aromatic, a compound must
meet both of the following criteria:
• It must have an un-interrupted cyclic π cloud
above & below the plane of the molecule
• The π cloud must contain (4n + 2) π electrons (n
= 0, 1, 2…)
un-interrupted
cyclic π cloud 
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  1. Chapter 8: ARENES Benzene 2
  2. Aromatic: (+) (-) (+) N O S H 4
  3. NOMENCLATURE OF MONOSUBSTITUTED BENZENES Name of substituent + benzene 6
  4. NOMENCLATURE OF DI- & POLYSUBSTITUTED BENZENES Alphabetical order, 1-position for the 1st stated substituent 8
  5. Alphabetical Lowest possible order numbers 10
  6. REACTIONS OF BENZENE Halogenations of benzene 12
  7. Nitration of benzene 14
  8. Reaction mechanism: electrophilic substitution 16
  9. Reaction mechanism: electrophilic substitution 22
  10. REACTIONS OF SUBSTITUTED BENZENES Relative rates of electrophilic substitutions: Electron- Electron- donating withdrawing 24
  11. EFFECTS OF SUBSTITUENTS ON ORIENTATION E/D group Only for halogen group 28
  12. E/D group 30
  13. THE ORTHO-PARA RATIO Increase in Decrease in the size of the o/p ratio substituents 32
  14. Aniline & N-substituted anilines do NOT undergo Friedel- Crafts reactions: More deactivating than halogen Also can NOT undergo nitration – primary amines are easily oxidized Phenol & anisole do undergo Friedel-Crafts reactions, orienting ortho & para – oxygen does NOT complex with the Lewis acid 34
  15. HALOGENATIONS OF ALKYL SUBSTITUENTS NOT Lewis acid Can undergo E1 & E2, SN1 & SN 2 reactions as usual 36
  16. NUCLEOPHILIC AROMATIC SUBSTITUTION REACTIONS E/W groups must be positioned ortho / para to the halogen 38