1. Organic Chemistry Reviews Chapter 14 Cindy Boulton March 22, 2009

2. 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

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 (-NH 2 )  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 HSO 3 attached  Nitrobenzene  Benzene with nitrite attached (-NO 2 )

6. Stability of Benzene  Stability of conjugate π systems  Pseudo π bond 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 sp 2 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