Organic Lecture 2/19

Review

  • Cycloheptatriene: one that’s aromatic is the cation because of 4n+2 electrons, satisfying Huckel’s rules.

  • Heterocycles can be aromatic as well: can re-hybridize to make aromatic.

  • Making benzene ring: 3 acetylenes, Cu or Fe, and heat


Reaction of Arenes

  • Generally unreactive, but if they do react it will happen via substitution. Require harsh conditions because of how stable an arene is.

  • Birch reduction: convert benzene into non-conjugated diene. Uses Na, NH3 and CH3OH.

Mechanism of Birch Reduction

-always forms more stable alkene, more substituted

Oxidized Arenes:

  • Usually resistant to oxidation because nothing can be pulled off. Much rather go through combustion.

  • Side Chain Oxidation: needs at least one benzylic hydrogen


Electrophilic Aromatic Substitutions (EAS):

  • The electrophile has to be ridiculously unstable for the pi bond on aromatic to come grab it.

  • Mechanism: generate electrophile (fast), form carbocation(slow), then regeneration of aromaticity(fast)


  • Electrophiles to use: Cl+, NO2+, C+(CH3)3, and SO3


Halogenation of Arenes: