1. Aromatic Compounds

2. Aromatic Systems are Characterized by Their Chemical Stability Note the chemical stability of the aromatic systems to the reaction conditions in the following slides

3. Note aromatic system’s stability toward hydrogenation

4. Note aromatic systems’ stability toward strong reducing agent LiAlH 4

5. Note the (two) aromatic systems’ stability toward Br 2

6. Note the aryl iodide’s stability toward S N 2 substitution (S N 2 substitution occurs at the sp3 hybridized carbon)

7. Note the aryl iodide’s stability toward the strong base (potassium tert-butoxide) used to effect elimination

8. Reactions of Aromatic Systems: Electrophilic Aromatic Substitution

15. The Friedel-Crafts Reaction

21. Treatment of Aryl Halides with Extremely strong bases (amide anions, NaNH 2, pKa of ammonia = 38) can cause substitution reactions… (note that the above table shows the conjugate acids only)

22. But the mechanism involves a two-step process of elimination-addition.

24. Treatment of aryl halides having strongly electron- withdrawing substituents (at the 2- and the 4-position) can also cause substitution reactions But…

25. The mechanism involves addition-elimination.

29. Reactions of Side Chains and Attached Functionality on Aromatic Compounds

31. Treatment of amines with nitrous acid (HONO) generates diazonium salts

33. The Sandmeyer Reaction Swiss chemist (1854-1922) after whom reaction is named

36. Benzylic Positions Can be Selectively Oxidized (all the way to the carboxylic acid) by Potassium Permanganate

40. The Clemmensen Reduction

43. Hydrogenolysis of Benzyl Esters and Benzyl Ethers