Organic Chemistry Overview

Introduction to Organic Chemistry

• Focuses on organic compounds containing carbon atoms.
• Carbon typically forms four bonds.

Key Elements and Their Bonding Preferences

• Hydrogen (H): 1 bond
• Beryllium (Be): 2 bonds
• Boron (B): 3 bonds
• Carbon (C): 4 bonds
• Nitrogen (N): 3 bonds
• Oxygen (O): 2 bonds
• Halogens (F, Cl, Br, I): 1 bond

Special Note on Halogens

• Halogens can form seven bonds in certain cases (not covered in this video).

Drawing Lewis Structures

• Understanding bonding preferences is crucial for drawing Lewis structures.

Example: Water (H2O)

• Oxygen: 2 bonds, Hydrogen: 1 bond
• Lewis structure: 1 oxygen with 2 hydrogen, 2 lone pairs on oxygen.
• Hydrogen Bond: Special type of covalent bond when H is attached to N, O, or F.
• Importance: Explains water’s high boiling point.

Example: Methyl Fluoride (CH3F)

• Carbon: 4 bonds, Fluorine: 1 bond, Hydrogens: 3
• Lewis structure includes 3 lone pairs on Fluorine.
• Polar Covalent Bond: Carbon (2.5) and Fluorine (4.0); electronegativity difference > 0.5.

Polar vs Nonpolar Bonds

• Polar Bond: Charged separation; one side positive, one side negative.
• Nonpolar Bond: Example includes carbon-hydrogen (C-H) bonds.
• Hydrocarbons (e.g., Methane CH4) are nonpolar due to equal sharing of electrons.

Types of Bonds

• Covalent Bond: Electrons shared (equally or unequally).
  • Nonpolar Covalent Bonds: Electrons shared equally (e.g., H2)
  • Polar Covalent Bonds: Electrons shared unequally (e.g., H-F).
• Ionic Bond: Electrons transferred; example includes Sodium (Na) and Chlorine (Cl).
  • Cation: Positively charged ion (e.g., Na+).
  • Anion: Negatively charged ion (e.g., Cl-).

Types of Organic Compounds

Alkanes (Saturated Compounds)

• General formula: CnH(2n+2)
• Examples:
  • Methane (C1H4)
  • Ethane (C2H6)
  • Propane (C3H8)
  • Butane (C4H10)
  • Pentane (C5H12)
  • Hexane (C6H14)
  • Heptane (C7H16)
  • Octane (C8H18)
  • Nonane (C9H20)
  • Decane (C10H22)

Alkenes (Unsaturated Compounds with Double Bonds)

• Example: Ethylene (C2H4)

Alkynes (Unsaturated Compounds with Triple Bonds)

• Example: Acetylene (C2H2)

Bond Lengths and Strengths

• Bond Lengths:

  • C-C single bond: longest (154 pm)
  • C-C double bond: shorter (133 pm)
  • C-C triple bond: shortest (120 pm)

• Bond Strengths:

  • Single bond: weakest
  • Triple bond: strongest

Sigma and Pi Bonds

• Single Bond: 1 sigma bond
• Double Bond: 1 sigma and 1 pi bond
• Triple Bond: 1 sigma and 2 pi bonds
• Strength: Sigma bonds > Pi bonds.

Hybridization of Carbon Atoms

• sp3: 4 groups
• sp2: 3 groups
• sp: 2 groups

Determining Hybridization

• Count the number of atoms and lone pairs.

Formal Charge Calculation

• Formula: Formal Charge = Valence Electrons - (Bonds + Nonbonding Electrons)
• Example with Carbon:
  • 4 valence electrons
  • Formal charge based on bonds and lone pairs.

Functional Groups in Organic Compounds

• Alcohols: -OH, e.g., ethanol (C2H5OH)
• Aldehydes: C=O + CH, e.g., acetaldehyde (C2H4O)
• Ethers: R-O-R, e.g., dimethyl ether (C2H6O)
• Ketones: C=O in the middle, e.g., propanone (C3H6O)
• Esters: RCOOR', e.g., methyl ethanoate (C3H6O2)
• Carboxylic Acids: COOH, e.g., pentanoic acid (C5H10O2)

Summary

• Understanding the bonding preferences, types of bonds, hybridization, and functional groups is essential for mastering organic chemistry.