Organic Chemistry Lecture Notes

Introduction

• The speaker conducted an experiment using reverse psychology by asking viewers not to watch the video.
• Audience engagement: Comments on reasons for watching the video requested.
• Focus: Introduction to organic chemistry, specifically drawing Lewis structures.

Lewis Structures Basics

• Periodic Table Groups:
  • Group 1: Hydrogen (H), Lithium (Li), Sodium (Na) - 1 valence electron, forms 1 bond.
  • Group 2: Beryllium (Be) - 2 valence electrons, forms 2 bonds.
  • Group 3A: Boron (B) - 3 valence electrons, typically forms 3 bonds.
  • Carbon (C): 4 valence electrons, forms 4 bonds.
  • Group 5A: Nitrogen (N) - 5 valence electrons, forms 3 bonds when neutral.
  • Group 6A: Oxygen (O) - 6 valence electrons, forms 2 bonds when neutral.
  • Group 7A: Fluorine (F) - 7 valence electrons, forms 1 bond.

Key Bonding Principles

• Octet Rule: Elements tend to form bonds to achieve 8 electrons in their outer shell.
• Exceptions: Some elements can form more or fewer bonds under certain conditions.
  • Nitrogen: Neutral state has 3 bonds, can gain or lose bonds to charge.
  • Oxygen: Neutral state has 2 bonds, can gain or lose bonds to charge.

Lewis Structure Examples

• Ammonia (NH3): 1 lone pair, 3 bonds.
• Water (H2O): 2 bonds, 2 lone pairs.
• Hydroxide (OH−): 1 bond, negative charge.
• Methane (CH4): 4 bonds from Carbon to 4 Hydrogens.
• Ethane (C2H6): 2 Carbons, each with 3 Hydrogens.
• Propane (C3H8): 3 Carbons, drawn sequentially.
• Alkanes: Saturated hydrocarbons with the formula CnH2n+2.
• Alkenes (C2H4): Contains double bonds, unsaturated, formula CnH2n.
• Alkynes (C2H2): Contains triple bonds, unsaturated, formula CnH2n-2.

Functional Groups and Naming

• Alcohols (R-OH): Example - Methanol (CH3OH).
• Ethers (R-O-R'): Example - Dimethyl ether (CH3OCH3).
• Aldehydes (R-CHO): Example - Ethanol (CH3CHO).
• Ketones (R-CO-R'): Example - Butanone (C4H8O).
• Carboxylic Acids (R-COOH): Example - Propanoic acid (C3H6O2).
• Esters (R-COO-R'): Example - Methyl ethanoate (CH3COOCH3).
• Amines (R-NH2): Example - Ethylamine.
• Amides (R-CONH2): Example - Butanamide.

Resonance Structures

• Definition: Different Lewis structures for the same molecule showing electron distribution.
• Notation: Curved arrows to indicate electron movement.
• Stability: Major vs. minor resonance contributors based on charge separation.

Formal Charge Calculation

• Formula: Formal Charge = Valence Electrons - (Bonds + Lone Pairs).
  • Example for Oxygen: 6 valence electrons - (1 bond + 6 dots) = -1 charge.

Conclusion

• Encouragement to explore further with provided links to additional resources and videos on organic chemistry topics such as naming compounds and drawing Lewis structures.