General Organic Chemistry (G.O.C) Energetics Session Notes Day 13/14 (Night Marathon Session by Wasim Sir) 🚀🔥🙌😍🙇‍♂️💕❤✨📘 👨‍🏫🖊🗒🥇🎓🍲💪 Telegram group: https://t.me/joinchat/HfgIYhxUDD4ImL7iwB-RGg

Key Concepts Covered and Discussed

Introduction to Session

• Importance of General Organic Chemistry
• Significance of understanding resonance, inductive effects, and hyperconjugation
• Emphasis on covering important chapters from scratch

Terms and Definitions

• Localized vs. Delocalized Electrons
  • Localized: Electrons shared between two atoms
  • Delocalized: Electrons shared among more than two atoms
• High Energy Electrons: Electrons subjected to less attraction by the nucleus, such as π-electrons
• Resonance: Delocalization of high energy electron pairs (π-electrons); leads to increased stability

Resonance

• True Structure: When a true structure (actual bond length, etc.) cannot be drawn, molecules exhibit resonance
• Conditions for Resonance: Presence of parallel p-orbitals with high energy electrons co-planar to each other
• Canonical Form (or Theoretical Structure): Proposed structures showing localized bonding but can't explain all properties
• Resonance Hybrid: Structure that contains delocalized bonding and explains all properties of the molecule
• Energy and Stability Orders:
  • Resonance hybrid is most stable due to delocalization
  • Stability ∝ Resonance energy

Critical Points on Resonance

1. Hybridization Influence
2. Electronegativity Relations
3. Conditions: Presence of parallel p-orbitals
4. Resonance energy: Stability increased due to lower potential energy
5. Canonical structures should have same energy, shared & unshared electron pairs
6. Delocalization Stability Order

Inductive Effect

• Definition: Partial polarization due to the transmission of σ-electrons through bonds due to electronegativity differences
• Importance: This effect weakens over distance and is only significant up to three carbon atoms
• Plus I: Electron donating (alkyl groups like -CH3, -C2H5)
• Minus I: Electron withdrawing (groups like -NO2, -CN, Halogens)
• Key Factors:
  • Effectiveness of +I or -I depending on position and relative electronegativity

Hyper Conjugation

• Definition: Sigma electron delocalization due to overlap of p-orbital of sp2 hybridized carbon with adjacent CH sigma bonds
• Types:
  1. σ-π Hyper-conjugation
  2. σ-Positive Hyper-conjugation
  3. σ-Odd electron Hyper-conjugation
• Sacrificial vs. Isovalent Hyper-conjugation:
  • Sacrificial: with charge-separated forms
  • Isovalent: without charge separation
• α-Hydrogen Contribution: Number of hyperconjugative structures equals the number of alpha hydrogens +1

Mesomeric Effect

• Definition: When attached groups cause charge separation through resonance
• Positive Mesomeric (π-electron donating): Groups like -NH2, -OH
• Negative Mesomeric (π-electron withdrawing): Groups like -NO2, -CN

S.I.R. (Steric Inhibition of Resonance)

• Definition: Steric hindrance reducing resonance effects leads to decreased extent of resonance
• Application: Explain bond lengths & angles, molecular stability due to repulsions and ineffective overlaps

Aromaticity

• Criteria for Aromatic Compounds:

  • Cyclic, planar conjugated systems
  • Follows Hückel's rule: 4n+2π electrons

• Anti-aromatic Criteria: 4nπ electrons

• Non-aromatic: Lack of planarity

• Examples: Benzene, Anthracene, Cyclooctatetraene

• Experimental Correlates: Observational definitions for stability

• Aromaticity Stability

• Effects Based on Overlaps, Planarity

Practice Questions

• Various types of stability, acidity, and basicity comparisons due to inductive, resonance, hyperconjugation, and mesomeric effects discussed

Important Series to Remember

1. Minus I Showing Groups
2. Plus I Showing Groups
3. Minus M Showing Groups
4. Plus M Showing Groups
5. Plus H Power Series
6. Minus H Power Series

Types of Questions Covered:

1. Stability order of carbocation
2. Stability order of carbanion
3. Acidic strength order (Kₐ order)
4. Basic strength order (Kᴮ order)
5. Bond length and angle comparisons based on inductive effect, resonance, hyperconjugation, and aromaticity

Notes Download Link

Transcription Notes GOC Day 13 Marathon Session Telegram group: https://t.me/joinchat/HfgIYhxUDD4ImL7iwB-RGg