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
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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- Chapter 8: ARENES Benzene 2
- Aromatic: (+) (-) (+) N O S H 4
- NOMENCLATURE OF MONOSUBSTITUTED BENZENES Name of substituent + benzene 6
- NOMENCLATURE OF DI- & POLYSUBSTITUTED BENZENES Alphabetical order, 1-position for the 1st stated substituent 8
- Alphabetical Lowest possible order numbers 10
- REACTIONS OF BENZENE Halogenations of benzene 12
- Nitration of benzene 14
- Reaction mechanism: electrophilic substitution 16
- Reaction mechanism: electrophilic substitution 22
- REACTIONS OF SUBSTITUTED BENZENES Relative rates of electrophilic substitutions: Electron- Electron- donating withdrawing 24
- EFFECTS OF SUBSTITUENTS ON ORIENTATION E/D group Only for halogen group 28
- E/D group 30
- THE ORTHO-PARA RATIO Increase in Decrease in the size of the o/p ratio substituents 32
- 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
- HALOGENATIONS OF ALKYL SUBSTITUENTS NOT Lewis acid Can undergo E1 & E2, SN1 & SN 2 reactions as usual 36
- NUCLEOPHILIC AROMATIC SUBSTITUTION REACTIONS E/W groups must be positioned ortho / para to the halogen 38