Organic Chemistry Fundamentals: Carbon-Based Bonding and Isomerism

What is Organic Chemistry?

• Definition: the study of carbon-based molecules and how they interact.
• Emphasis in lecture: reactions involve movement and redistribution of electrons; bonds are broken and formed between carbon-based molecules.
• The recording captures both PowerPoint content and material written on the board.
• If pace is fast, don’t worry; the notes are provided to supplement understanding.

Why Carbon Chemistry Matters

• Carbon-based life forms on Earth.
• Many everyday materials are carbon-based: what we eat, the clothes we wear, drugs, plastics, and other materials.
• Although not absolute, ionic species are often classified as inorganic; example: ammonium ion and cyanate ion.
• Example ionic species:
  • Ammonium: $ext{NH}_4^+$
  • Cyanate: $ext{OCN}^-$ (note: the formal negative charge is placed on the oxygen in this example; resonance can distribute charge)
• The other contrasted case shows a molecule with all covalent bonds (no ionic bonds).

Carbon-based Molecules and Isomerism

• In carbon chemistry, different arrangements of the same atoms can lead to different molecules.
• Key concept: constitutional isomers (same molecular formula, different connectivity).
• Example: for $ext{C}<em>2 ext{H}</em>6 ext{O}$ there are two distinct constitutional isomers:
  • Ethanol: $ext{CH}<em>3 ext{CH}</em>2 ext{OH}$
  • Dimethyl ether: $ext{CH}<em>3 ext{OCH}</em>3$
• Both have the same atoms, but bonds connect them differently, giving different properties and reactivities.

Structural Theory of Matter and Bonding

• Atoms form covalent bonds; nonmetals commonly form covalent bonds.
• Typical bonding patterns (for neutral molecules):
  • Carbon: usually forms $4$ bonds
  • Nitrogen: usually forms $3$ bonds
  • Oxygen: usually forms $2$