Organic Chemistry Lecture Notes

Welcome and Introductory Remarks

• Abhishek Sir welcoming students
• Reminder: Share if you find the video helpful
• Upcoming ICT lecture around exam time

Lecture Focus: Organic Chemistry (Halogen Derivatives)

Key Topics

• Halogen Derivatives: Introduction, marks allocation, importance
• Classification: Understanding through Norman Nomenclature, IUPAC
• Physical and Optical Properties: Only optical property is examined
• Reactions with Active Metals: Focus for this lecture

Classification of Halogen Derivatives

• Based on Hydrocarbon Skeleton
• Hydrocarbon (Group 17 - Halogens)
  • Halogens: Fluorine, Chlorine, Bromine, Iodine
  • Replacing Hydrogen with Halogen leads to Halogen Derivatives
• Types of Halogen Derivatives:
  • Haloalkane (Single bond)
  • Haloalkene (Double bond)
  • Haloalkyne (Triple bond)
  • Haloarene (Benzene ring)

Further Classifications

• Monohalogen compounds:
  • Primary (1°) - Attached to one carbon
  • Secondary (2°) - Attached to two carbons
  • Tertiary (3°) - Attached to three carbons
• Aromatic Compounds

Methods of Preparation

• From Alcohols: Using HCl, ZnCl₂ (Lucas Reagent)
• Using Phosphorus: PCl₃, PCl₅, SOCl₂
• Reaction Mechanisms: Focus on reactions and by-products

Reaction with Halogen Acids

• Alcohols + HX: Forms alkyl halides, e.g., ROH + HCl -> RCl + H₂O
  • Anhydrous ZnCl₂: Acts as a catalyst
  • Lucas Reagent: Mixture of HCl + ZnCl₂

Optical Properties

• Understanding the optical activity and enantiomers
• Chiral Carbon: A carbon with four different substituents
• Enantiomers: Non-superimposable mirror images
• Optical Isomerism: Isomers differing in rotation of polarized light

Chemical Properties

• Nucleophilic Substitution: SN1 and SN2 mechanisms
  • SN1: Unimolecular, two-step, formation of carbocation
  • SN2: Bimolecular, single-step, backside attack

Elimination Reactions

• Dehydrohalogenation: Removal of HX
  • Formation of alkenes
  • E1 and E2 mechanisms

Special Reactions

• Grignard Reagents: RMgX formation and reactions
• Wurtz Reaction: Formation of higher alkanes using NA and RX

Resonance Effect

• Understanding resonance structures and their stability
• Rules for Resonance: Negative charge moves, avoid double bond next to it

Substitutions Reactions with Benzene

• Friedel-Crafts Alkylation/Acylation: Introduction of alkyl/acyl groups into benzene ring
• Electrophilic Substitution: Halogenation, nitration
• Resonance stabilization: Positions 2 and 4 are major sites for substitution

Summarizing Key Points

• Preparation methods, mechanisms, optical isomerism, special reactions, substitution reactions with benzene
• Emphasis on understanding the principles and mechanisms

Final Remarks

• Importance of understanding and practicing these reactions
• Encouragement to keep revising and stay focused on exams