NOMENCLATURE OF MONOSUBSTITUTED BENZENES Name of substituent + benzene... PREPARATION OF BENZENE Petroleum Bezene... REACTIONS OF BENZENE Halogenations of benzene... Reaction mechanism:
Trang 2Benzene
Trang 3CRITERIA 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
Trang 5cloud
Trang 6NOMENCLATURE OF MONOSUBSTITUTED BENZENES
Name of substituent + benzene
Trang 7Names have to be memorized:
Trang 10Alphabetical
order
Lowest possible numbers
Trang 11PREPARATION OF BENZENE
Petroleum Bezene
Trang 12REACTIONS OF BENZENE
Halogenations of benzene
Trang 13Reaction mechanism: electrophilic substitution
Catalyst regeneration
Trang 14Nitration of benzene
Trang 15Sulfonation of benzene
Reversible reaction
Trang 16Reaction mechanism: electrophilic substitution
Trang 17Friedel-Crafts Alkylations of benzene
Trang 1818
Trang 19Carbocation rearrangement
Trang 2020
Trang 21Friedel-Crafts Acylations of benzene
Trang 22Reaction mechanism: electrophilic substitution
Trang 23Rearrangement
Trang 24Electron- withdrawing
Trang 2626
Trang 29E/W
group
Trang 30E/D
group
Trang 31E/W
group
Trang 33ADDITIONAL CONSIDERATIONS
More deactivating than halogen, the ring is too unreactive for
(only) Friedel-Crafts alkylations & acylations
Trang 34Aniline & N-substituted anilines do NOT undergo Friedel- Crafts reactions:
More deactivating than
halogen
Phenol & anisole do undergo Friedel-Crafts reactions, orienting ortho & para – oxygen does NOT complex with
the Lewis acid
Also can NOT undergo nitration –
primary amines are easily oxidized
Trang 35SYNTHESIS OF TRISUBSTITUTED BENZENES
More activating substituent controls the regioselectivity
Trang 36HALOGENATIONS OF ALKYL
SUBSTITUENTS
NOT Lewis acid
Can undergo E1 & E2, S N 1 & S N 2 reactions as usual
Trang 37OXIDATIONS OF ALKYL SUBSTITUENTS
Trang 38NUCLEOPHILIC AROMATIC SUBSTITUTION REACTIONS
E/W groups must be positioned ortho / para to the halogen
Trang 39The greater the number of E/W substituents, the easier it is
to carry out the reaction
Trang 4040