Chapter 4: Aromatic Compounds and Reactions of Alkynes and Benzene

Chapter 4: Aromatic Compounds. Benzene Br₂ + X → doesn't happen! that because it's not an alkene! Cyclic Planar 6 π electrons ΔH (kcal/mol) -120 -116 H₂ -28.6 -49.8 (more stable) 3 x -28.6 = -85.8 kcal/mol -658 + (-85.8) = -36 kcal/mol Resonance energy = Stabilization energy CH3-CH2-C≡C-CH3 + H₂ → CH3-CH2-CH=CH-CH3 Lindlar's catalyst CH3-CH2-C≡C-CH3 + H₂ → CH3-CH2-CH₂-CH3 H₂ Pt/Pd CH3-C≡C-H + H₂O, H₂SO₄, HgSO₄ → CH3-C-CH3 O || CH3 (ketone) CH3-C≡C-CH3 + H₂O, H₂SO₄, HgSO₄ → CH3-C-CH3 || OH CH3 (enol) CH3-C≡C-CH3 + HBr → CH3-CH=C-CH3 | Br CH3-C≡C-CH3 + HBr → CH3-CBr=CH2 | H CH3-C≡C-CH3 + HBr, H₂O₂ → CH3-CH2-CBr=CH2 CH3-C≡C-CH3 + NH₃ → CH3-C=C-CH3 | NH₂ (nucleophilic addition) Acidity: sp > sp² > sp³ Polarity: sp > sp² > sp³ 3.20: Adding reactions for alkynes: Halogenation: CH₃-C≡C-CH₃ + Br₂ → Br-CH=C-CH₃ Br CH₃-C≡C-CH₃ + excess Br₂ → Br-CH-C-CH₃ Br | Br Hydrohalogenation: CH₃-C≡C-H + HBr → CH₃-C=CH₂ | Br (Markovnikov) CH₃-C≡C-CH₃ + excess HBr → CH₃-CBr₂-CH₃ CH₃-C≡C-CH₃ + HCl → CH₃-C=CH₂ | Cl CH₃-C≡C-CH₃ + excess HCl → CH₃-CCl₂-CH₃ CH₃-C≡C-CH₃ + HCl, H₂O₂ → CH₃-CH₂-CCl=CH₂ Symmetric, no isomers CH₃-C≡C-CH₃ + excess HCl, H₂O₂ → CH₃-CH₂-CCl₂-CH₃ 2 products Hydrogenation: CH₃-C≡C-H + H₂ → CH₃-CH=CH₂ Ni CH₃-C≡C-CH₃ + H₂ → CH₃-CH₂-CH₂-CH₃ Pd/C CH₃-C≡C-CH₃ + H₂ → CH₃-CH=CH-CH₃ Lindlar's catalyst (cis only) Chemoselective for a triple bond, and stereospecific. Naming of benzene compounds: Benzene Mono-substituted benzene: Benzene < Toluene < Aniline < Phenol < CH₃ NH₂ OH Priority on naming is shown by the greater/less than sign. CHO CO₂H Benzaldehyde Benzoic acid Special name alone: OCH₃ CH=CH₂ C=O Anisole Styrene Acetophenone No priority: NO₂ Cl CH₂CH₃ Nitrobenzene Chlorobenzene Propylbenzene Di-substituted benzene: Br OH NH₂ 2-Bromotoluene 3-Nitrophenol 4-Methylaniline OH CHO OH 2-Aminophenol 3-Hydroxybenzaldehyde 2-Formylbenzoic acid OH CHO OH 2-Hydroxybenzaldehyde 3-Hydroxybenzaldehyde 2-Formylbenzoic acid OH CHO OH 2-Aminophenol 3-Aminophenol 4-Aminophenol OH CHO CO₂H 2-Hydroxybenzoic acid 3-Hydroxybenzoic acid 2-Formylbenzoic acid OH CHO CO₂H o-Hydroxybenzoic acid m-Hydroxybenzoic acid o-Formylbenzoic acid OH CHO CO₂H o-Aminophenol m-Aminophenol p-Aminophenol **Naming of Benzene Compounds** **Mono-substituted benzene:** NO₂ Br 1-Bromo-3-nitrobenzene m-Bromonitrobenzene Br F 1-Fluoro-2-propylbenzene o-Fluoro-propylbenzene OH OH 1,2-Dihydroxybenzene o-Dihydroxybenzene OH OH 1,4-Dihydroxybenzene p-Dihydroxybenzene CH₃ CH₃ 1,4-Dimethylbenzene p-Xylene **Tri-substituted or more:** OH Br CH₃ 2-Chloro-4-methylphenol Cl Cl NO₂ 4-Chloro-2-ethyl-1-ethylbenzene OH OH OH 1,3,5-Trihydroxybenzene NO₂ NO₂ NO₂ 2,4,6-Trinitrotoluene CH₃ CH₃ C₆H₅ 3-Ethyl-4-phenylhexane