Lecture Notes: Hello Alkanes and Hello Arenes
Introduction
- Welcome and enthusiasm for preparation
- TodayтАЩs lecture will cover Hello Alkanes and Hello Arenes
- Objective: Bring a smoky flare to life
Hello Alkanes and Hello Arenes
First Method: Preparation from Alcohol
- Reaction: Alcohol with HX
- Reaction Formation
- ROH + HX --> RX + H2O
- Organic framework alteration with halogen addition
- Organic Rearrangement Possibilities
- 123 Hydride shift and Methyl shift expansion
Second Method: Preparation from Silver Salts of Fatty Acids
- Reaction: With Ethanoyl Chloride
- Reaction Formation
- R-COOAg + Cl2 --> RCl + CO2 + AgCl
Preparation from Alkyl halides (Sandmeyer Reaction)
- Reaction: RN2+X-
- Cu2Cl2/HCl or Cu2Br2/HBr
- RN2+X- --> RX + N2 (gas)
- Example: C6H5N2+Cl- + Cu2Cl2/HCl --> C6H5Cl + N2
Important Points on Reactions
- Rearrangement in Reactions
- Some reactions may involve rearrangement like Hydride shift, and Methyl shift.
- Protonation step
- Protonation is crucial for certain reactions involving alcohols.
- Use of Protective Groups
- Some reactions utilize protective groups for selective transformations.
Famous Reactions
SN1 (Substitution Nucleophilic Unimolecular)
- First Step: Formation of carbocation, slow and reversible.
- Second Step: Nucleophile attacks the carbocation, fast.
- Rate: Depends on the stability of the carbocation.
- Stereochemical Outcome: Racemization of configuration due to planar intermediate.
SN2 (Substitution Nucleophilic Bimolecular)
- Reaction Mechanism: Backside attack by nucleophile.
- Stereochemical Outcome: Inversion of configuration.
- Rate Determining Step: One-step process involving both substrate and nucleophile.
- Example: CH3-Cl + OH- --> CH3OH + Cl-
Commonly Used Reagents
- Preparation of RX from ROH
- HX (acid halides), PCl5, SOCl2
- Sandmeyer Reaction
- Cu2Cl2/HCl, Cu2Br2/HBr for C6H5X formation
Problem Solving Examples:
Example 1: Conversion of Benzoic Acid to Benzyl Chloride.
- Reagents: SOCl2, Nucleophilic substitution to form benzyl chloride.
Example 2: Nitration of Chlorobenzene
- Reagents: HNO3, H2SO4
- Product: o-Nitrochlorobenzene, p-Nitrochlorobenzene
Notes on Complex Examples
Side Reactions and By-products
- By-products in reactions with different conditions and reagents
Reaction Sequence Analysis
- Detailed steps for complex reaction mechanisms
Conclusion
- Revision and clarification of possible doubts
- Next Lecture: Regular revision and exam preparation
Tips for Quick Revision:
- Use flowcharts for mechanisms
- Summarize key points for each reaction type
Summary
- Thorough understanding of reaction mechanisms and preparations
- Importance of identifying and handling rearrangements and protective groups
Practice regularly and keep revising important examples.