Lecture Notes: Chemical Bonding of Organic Compounds

Introduction

• Organic vs Inorganic Compounds
  • Organic: Composed of carbon & hydrogen; decomposed by heating (combustion reactions).
  • Inorganic: Composed of metals & non-metals; not easily decomposed by heating.

Characteristics of Organic Compounds

• Tend to be molecular and neutral.
• Composed of elements: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur, Phosphorus.
• Can be found in solid, liquid, and gas forms.
• Solubility in water depends on molecular size and composition.

Special Characteristics of Carbon

• Bonds to four atoms; bonds are strong and non-reactive.
• Can form long chains or rings (e.g., cyclohexane).
• Forms single, double, or triple bonds.
• Bond energies: Carbon-carbon bonds are stronger than sulfur-sulfur or silicon-silicon bonds.

Chemical Bonds Overview

• Ionic Bonds: Transfer of electrons from metal to non-metal, forming cations and anions.
• Covalent Bonds: Sharing of electrons between non-metal atoms.
  • Can be shown as lines representing electrons shared.
  • Types: Single, double, triple bonds.

Electronegativity and Polarity

• Electronegativity: Ability of an atom to attract shared electrons.
• Polar vs Nonpolar Bonds
  • Nonpolar: Electronegative difference < 0.5.
  • Polar: Difference between 0.5 and 1.9.
  • Ionic: Difference > 1.9.

Examples

• Hydrogen and Fluorine: Polar bond.
• Oxygen and Hydrogen: Polar bond.
• Nitrogen and Hydrogen: Polar bond.
• Carbon and Hydrogen: Nonpolar bond.
• Sodium Chloride: Ionic bond.

Bond Types

• Ionic Bonds: Between metal and non-metal (e.g., NaCl).
• Nonpolar Covalent Bonds: Between identical atoms (e.g., H2, O2).
• Polar Covalent Bonds: Between atoms with different electronegativities (e.g., HCl).

Bond Strength and Length

• Single bonds: Longest and weakest.
• Double bonds: Shorter and stronger.
• Triple bonds: Shortest and strongest.

Electronegativity Trend

• Increases across a period and decreases down a group.

Problem Solving

• Use electronegativity to determine bond type and polarity.
• Using delta notation to indicate electronegativity differences.

Conclusion

• Distinguishing between bond types and understanding their properties is crucial for understanding organic chemistry.
• The next lecture will cover organic chemical structures.