Lecture Notes on Organic Chemistry Revision

Key Topics Covered:

• Electrophilic Addition Reactions
• Electrophilic Substitution Reactions
• Nucleophilic Substitution Reactions (SN1 and SN2)
• Nucleophilic Addition Reactions
• Elimination Reactions (E2, E1, E1cB)
• Named Reactions
• Organic Chemistry Mechanisms and Examples
• Bio-Molecules

Electrophilic Addition Reactions

1. H-X Addition:
   • Formation of carbocation.
   • Shift possible.
   • Reactivity depends on carbocation stability.
2. H-Br and Peroxide Effect (Anti-Markovnikov):
   • Only for HBr with peroxides.
   • Free radical mechanism.
3. Concentrated vs Dilute H₂SO₄:
   • Concentrated: SO₃H addition.
   • Dilute: H₂O addition.
4. Br₂/CCl₄ or Br₂/H₂O:
   • Br₂/CCl₄: Non-classical carbocation, anti-addition.
   • Br₂/H₂O: Forms halohydrin.
5. Oxidation-rHgO:
   • Mercuration-Demercuration (Oxymercuration-Demercuration).
6. Hydroboration-Oxidation:
   • Anti-Markovnikov, OH on less substituted carbon.
7. Cold KMnO₄:
   • Syn addition of OH groups.
8. Ozonolysis:
   • Reductive: O₃, Zn/H₂O → ketones and/or aldehydes.
   • Oxidative: O₃, H₂O₂ → carboxylic acids.

Electrophilic Substitution Reactions (ESR)

1. Friedel-Crafts Alkylation/Arylation:
2. Halogenation (Br₂/FeBr₃):
3. Nitration (HNO₃ + H₂SO₄):
4. Sulfonation (H₂SO₄):
5. Riemer-Tiemann Reaction:
6. Kolbe's Reaction:
7. Electrophilic Substitution Mechanism:
   • RDS: Formation of sigma complex.
   • Fast step: Loss of H⁺.
8. Activating/Deactivating Groups:

Nucleophilic Substitution Reactions

SN1 Mechanism:

• Formation of carbocation.
• Rate depends only on the concentration of the substrate (unimolecular).
• Order: 3° > 2° > 1° alkyl halides.
• Solvent: Polar protic.

SN2 Mechanism:

• Backside attack of nucleophile; simultaneous bond forming/breaking.
• Rate depends on the concentration of both substrate and nucleophile (bimolecular).
• Order: 1° > 2° > 3° alkyl halides (steric factors).
• Solvent: Polar aprotic.
• Inversion: Walden inversion.

Elimination Reactions

E1 Reaction:

• Formation of carbocation.
• Rate depends on the concentration of the substrate.

E2 Reaction:

• Single step.
• Proton abstracted by base, double bond formation, loss of leaving group.
• Reactivity Order: 3° > 2° > 1° alkyl halides.
• Base: Strong, bulky bases favor E2 over SN2.

E1cB Reaction:

• Anionic intermediate formation.
• Base: Weak base, poor leaving group, stable anion intermediate.

Named Reactions

1. Wolff-Kishner: Hydrazine, KOH, heat to reduce =O.
2. Cannizaro: Concentrated base, no α-hydrogens.
3. Aldol: α-hydrogens, base/acid, heat to eliminate.
4. Kolbe-Schmidt: Soda lime (NaOH, CaO) decarboxylation.
5. Rosenmund: H₂, Pd/BaSO₄, quinoline for acyl chloride reduction to aldehyde.
6. Claisen Condensation: Ester + Ester under base, β-keto ester.

Bio-Molecules

1. Amino Acids: Isoelectric point, Zwitterion.
2. Carbohydrates: Reducing vs Non-Reducing Sugars.
3. Nucleic Acids: DNA/RNA Structures.