Organic Chemistry Lecture Notes

Introduction

• Focus on organic compounds containing carbon atoms
• Carbon forms 4 bonds
• Understanding bond preferences of other elements is crucial

Element 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 (can form up to 7 bonds in special cases)

Lewis Structures

• Essential for understanding molecular structure
• Water (H2O): Oxygen forms 2 bonds, 2 lone pairs
• Methyl Fluoride (CH3F): Carbon forms 4 bonds, Fluorine forms 1 bond

Covalent Bonds

• Types:
  • Non-polar (e.g., Methane, CH4)
  • Polar (differences in electronegativity > 0.5, e.g., Carbon-Fluorine bond)
  • Hydrogen bonds (H attached to N, O, F)

Ionic Bonds

• Electrons are transferred, e.g., Sodium Chloride
• Cation: Positively charged ion, e.g., Sodium becomes Na+
• Anion: Negatively charged ion, e.g., Chlorine becomes Cl-

Alkanes and Alkenes

• Alkanes: Saturated, formula CnH2n+2
  • Methane (1C), Ethane (2C), Propane (3C), Butane (4C)
• Alkenes: At least one double bond, e.g., Ethene
• Alkynes: Triple bonds, e.g., Ethyne (Acetylene)

Bond Length and Strength

• Single bonds: Longest, weakest
• Double bonds: Intermediate
• Triple bonds: Shortest, strongest
• Sigma bonds: Stronger than pi bonds

Hybridization

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

Formal Charge

• Formula: Valence electrons - (Bonds + Dots)
• Positive, negative, and neutral charges

Functional Groups

• Alcohols: Contain OH, e.g., Ethanol
• Aldehydes: Carbonyl group at chain end, e.g., Ethanal
• Ketones: Carbonyl group within chain, e.g., Propanone
• Ethers: Oxygen between carbons, e.g., Dimethyl ether
• Carboxylic acids: COOH group, e.g., Pentanoic acid
• Esters: COO group, e.g., Methyl ethanoate

Structural Expansion

• Understanding condensed formulas and expanding them into full structures
• Position groupings: CH3 at ends, CH2 in middle

Summary

• Organic chemistry requires understanding of element bonding, molecule structure (Lewis structures), types of bonds, hybridization, and functional groups.
• Knowledge of these concepts aids in drawing molecular structures, predicting molecular properties, and understanding reactivity.