Organic Chemistry Lecture Notes

Introduction to Organic Chemistry

• Focus: Organic compounds containing carbon atoms
• Carbon typically forms four bonds

Bonds Formed by 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

Drawing Lewis Structures

• Importance of knowing bonds formed by elements
• Example: Water (H2O)
  • Oxygen forms 2 bonds, Hydrogen forms 1
  • Oxygen needs 8 electrons total, therefore 2 lone pairs are added
• Example: Methyl Fluoride
  • Carbon forms 4 bonds, Hydrogen & Fluorine form 1 bond each
  • Fluorine has 3 lone pairs

Types of Covalent Bonds

• Nonpolar Covalent Bonds: Equal sharing of electrons (e.g., C-H)
• Polar Covalent Bonds: Unequal sharing of electrons (e.g., C-F)
  • Electronegativity difference ≥ 0.5 indicates polarity
• Hydrogen Bonds: Special polar covalent bond when H is attached to N, O, or F

Ionic Bonds

• Formation: Transfer of electrons
• Example: Sodium and Chlorine
  • Sodium (metal) gives electron to Chlorine (non-metal)
  • Formation of cation (Na+) and anion (Cl-)

Alkanes and Saturated Compounds

• Alkanes: Saturated hydrocarbons (CnH2n+2)
  • Examples:
    • Methane (CH4)
    • Ethane (C2H6)
    • Propane (C3H8)
    • Butane (C4H10)

Alkenes and Alkynes

• Alkenes: Hydrocarbons with double bonds (e.g., Ethene C2H4)
• Alkynes: Hydrocarbons with triple bonds (e.g., Ethyne C2H2)
• Bond Lengths: Single > Double > Triple
• Bond Strengths: Triple > Double > Single

Sigma (σ) and Pi (π) Bonds

• Single Bond: 1 σ bond
• Double Bond: 1 σ and 1 π bond
• Triple Bond: 1 σ and 2 π bonds

Hybridization

• Determined by atoms/lone pairs attached to carbon
• Examples:
  • 4 groups: sp3
  • 3 groups: sp2
  • 2 groups: sp

Bonding Summary

• Sigma Bonds: Stronger than Pi Bonds
• Bond Order:
  • Single Bond: 1
  • Double Bond: 2
  • Triple Bond: 3

Formal Charge Calculation

• Formula: Valence electrons - (Number of bonds + dots)
  • Example: Carbon (4 valence electrons, 3 bonds) = +1 charge
• Ions:
  • Cations: Positive
  • Anions: Negative

Functional Groups and Organic Compounds

• Alcohols: -OH group (e.g., Ethanol)
• Aldehydes: Carbonyl group at chain end (e.g., Ethanal)
• Ketones: Carbonyl group in chain middle (e.g., Propanone)
• Esters: R-COO-R' (e.g., Methyl Ethanoate)
• Carboxylic Acids: COOH group (e.g., Pentanoic Acid)

Expanding Structures

• Practice with condensed formulas
• Methyl Groups: CH3 typically ends chains
• CH2 Groups: In the middle of chains
• Branching: CH groups with special elements