Organic Chemistry Lecture Notes

Overview

• Focus on organic compounds containing carbon atoms
• Carbon forms four bonds

Bonding Preferences

• 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, but can form more in different contexts

Lewis Structures

• Drawing Lewis structures involves knowing preferred bonds for each element
• Example: Water (H₂O) - Oxygen forms 2 bonds, Hydrogen 1 bond; add lone pairs to oxygen
• Hydrogen Bonds: Special covalent bond when H links to N, O, or F
• Polar Bonds: Uneven electron sharing due to electronegativity differences

Types of Bonds

• Polar Covalent Bonds: Unequal sharing, e.g., C-F bond
• Non-Polar Covalent Bonds: Equal sharing, e.g., C-H bond
• Ionic Bonds: Electron transfer, e.g., NaCl

Alkanes, Alkenes, and Alkynes

• Alkanes: Saturated, single bonds, formula CnH2n+2
  • Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈)
• Alkenes: At least one double bond
  • Example: Ethene (C₂H₄)
• Alkynes: At least one triple bond
  • Example: Ethyne (C₂H₂)

Bond Characteristics

• Bond Length: Single > Double > Triple
• Bond Strength: Triple > Double > Single
• Sigma (σ) and Pi (π) Bonds:
  • Single: 1σ
  • Double: 1σ + 1π
  • Triple: 1σ + 2π

Hybridization

• Based on number of attached atoms/lone pairs
  • sp³: 4 groups
  • sp²: 3 groups
  • sp: 2 groups

Formal Charge Calculation

• Formula: Valence electrons - (bonds + lone pair electrons)
• Examples:
  • Carbocation, carbanion

Functional Groups

• Alcohols: OH groups, e.g., Ethanol
• Aldehydes: Carbonyl group at end, e.g., Ethanal
• Ketones: Carbonyl group in middle, e.g., Propanone
• Esters: Two oxygens, one with a carbonyl, e.g., Methyl ethanoate
• Carboxylic Acids: Carbonyl + hydroxyl, e.g., Pentanoic acid

Structure Expansion

• Methyl (CH₃), methylene (CH₂), and chiral centers
• Example exercises on expanding condensed formulas

Tips

• Use periodic table for valence electrons
• Practice drawing structures based on bonding rules
• Understand functional groups and their naming conventions

Additional Resources

• Look up organic chemistry playlists for more detailed videos on various topics.