Organic Chemistry Lecture Notes

Introduction to Organic Chemistry

• Focuses on organic compounds containing carbon atoms.
• Carbon forms four bonds; important to know bonding preferences of other elements:
  • Hydrogen: 1 bond
  • Beryllium: 2 bonds
  • Boron: 3 bonds
  • Carbon: 4 bonds
  • Nitrogen: 3 bonds
  • Oxygen: 2 bonds
  • Halogens (Fluorine, Chlorine, Bromine, Iodine): 1 bond (typically)

Lewis Structures

• Water (H2O): Oxygen forms two bonds, with two lone pairs.
• Methyl Fluoride (CH3F): Carbon in middle; fluorine has three lone pairs.
• Bond Stability:
  • Polar bonds when electronegativity difference ≥ 0.5.
  • Non-polar bonds with difference < 0.5 (e.g., C-H bonds in methane).

Types of Bonds

• Covalent Bonds:
  • Polar Covalent Bonds: Unequal sharing of electrons (e.g., H-F).
  • Non-polar Covalent Bonds: Equal sharing (e.g., H-H).
• Ionic Bonds: Transfer of electrons (e.g., NaCl).

Alkanes and Alkenes

• Alkanes: Saturated hydrocarbons (CnH2n+2).
  • Examples: Methane (CH4), Ethane (C2H6), Propane (C3H8).
• Alkenes: Contain at least one double bond (e.g., Ethene, C2H4).
• Alkynes: Contain triple bonds (e.g., Ethyne, C2H2).

Bond Properties

• Length: Single bonds > double bonds > triple bonds.
• Strength: Triple bonds > double bonds > single bonds.
• Sigma and Pi Bonds:
  • Single bond = 1 σ bond.
  • Double bond = 1 σ + 1 π bond.
  • Triple bond = 1 σ + 2 π bonds.

Bond Order

• Single bond: Order 1
• Double bond: Order 2
• Triple bond: Order 3

Hybridization

• Determined by number of atoms and lone pairs around carbon.
  • sp3: 4 groups
  • sp2: 3 groups
  • sp: 2 groups

Formal Charges

• Formula: Valence electrons - (bonds + dots)
• Determine charges for stability analysis.

Functional Groups

• Alcohols: Contains -OH group (e.g., Ethanol)
• Aldehydes: Carbonyl group at end (e.g., Ethanal)
• Ketones: Carbonyl group in middle (e.g., Propanone)
• Ethers: Oxygen between carbons (e.g., Dimethyl ether)
• Carboxylic Acids: COOH group (e.g., Pentanoic acid)
• Esters: R-COO-R' (e.g., Methyl ethanoate)

Expanding Condensed Structures

• Practice breaking down condensed formulas into full Lewis structures.
• Identify functional groups and carbon chain structure.

Additional Topics

• Bonding electrons vs. non-bonding electrons.
• Resources for further study: YouTube organic chemistry playlists.