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Organic Chemistry Reviews Chapter 14

Organic Chemistry Reviews Chapter 14. Cindy Boulton March 22, 2009. Aromatic Compounds. Benzene 6 member ring 6 π electrons Alternating Double Bonds Resonance Hybrid All bonds 1 ½ - same length Only as many Hydrogen Atoms as Carbon Atoms. Nomenclature of Benzene Derivatives.

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Organic Chemistry Reviews Chapter 14

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  1. Organic Chemistry ReviewsChapter 14 Cindy Boulton March 22, 2009

  2. Aromatic Compounds • Benzene • 6 member ring • 6 πelectrons • Alternating Double Bonds • Resonance Hybrid • All bonds 1 ½ - same length • Only as many Hydrogen Atoms as Carbon Atoms

  3. Nomenclature of Benzene Derivatives • Disubstituted Benzene • Ortho: 1,2 • Meta: 1,3 • Para: 1,4 • Phenyl • group name of a benzene attached to a parent chain • Toluene • Benzene with one methyl group attached • Xylene • Benzene with two methyl groups attached • Ortho, meta, or para • Phenol • Benzene with a hydroxyl group attached (-OH) • Alcohol

  4. Nomenclature of Benzene Derivatives • Aniline • Benzene with a amine group attached (-NH2) • Anisole • Benzene with an ether bond to a methyl group • Phenly-O-Methyl • Acetophenone • Benzene with an acetyl group attached • Phenyl-(C=O)-Methyl • Benzaldehyde: formyl group attached, Phenyl-(C=O)-H • Oil of bitter almond • Benzophenone: two benzene rings attached, Phenyl-(C=O)-Phenyl

  5. Nomenclature of Benzene Derivatives • Benzoic Acid • Benzene with a carboxyl group attached, Phenyl-(C=O)-OH • Benzenesulfonic Acid • Benzene with HSO3 attached • Nitrobenzene • Benzene with nitrite attached (-NO2)

  6. Stability of Benzene • Stability of conjugate π systems • Pseudo πbond is formed • Some of the π electron density is delocalized • The π bond is spread out and becomes harder to react • More stable • Stability of aromatic compounds • Resonance stabilizaion • Forms a resonance hybrid • Delocalization of electrons by molecular orbitals • The π bond electrons are completely delocalized

  7. Aromatic Compounds • Aromatic Rules • 1) Cyclic • 2) Planar • P-orbitals have to line up to from π bonds • 3) A Huckle Number of Delocalizable electrons • Huckle Number = 6,10,14,18,… • All sp2 Carbons and alternating double bonds • Annulene • Benzene = [6] annulene • Benzoid Polycyclic aromatic • 6-member rings fused together • Non-Benzoid Polycyclic aromatic • Non 6-member rings fused together (=12)

  8. Heteroatomic Aromatics • Not Carbon • Follow Aromatic Rules: • Cyclic • Planar • Delocalizable electrons (Huckle Number) • Lone pair • Can be planar, perpendicular to ring, with other electrons to be counted as delocalizable electrons • Can be non-planar, not perpendicular, and not delocalizable depending on geometry of molecule • Pyridine, Furan, Pyrole, Thiophene

  9. Aromatic Compounds with Charge • 5-Carbon ring • 4 delocalizable electrons + Electron pair = 6 delocalizable electrons • Negative Charge • 7-Carbon ring • 6 delocalizable electrons + vacant orbital = 6 delocalizable elcetrons • Positive Charge

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