Overview
This lecture introduces the basic concepts of organic chemistry, focusing on carbon's atomic structure, its bonding behavior, and how it forms a variety of compounds.
Objectives of Organic Chemistry
- Describe the atomic structure of carbon.
- Explain how carbon's structure influences the types of bonds it forms.
- Recognize how carbon bonds with itself and with other elements to create diverse compounds.
Defining Organic Compounds
- To chemists, "organic" means any compound containing carbon, often with hydrogen, oxygen, nitrogen, phosphorus, or sulfur.
- Organic chemistry is the study of carbon-containing compounds, a major branch of chemistry.
- Organic compounds are common in everyday items, living organisms, and the environment.
Organic vs. Inorganic Compounds
- Organic compounds mostly have covalent bonds (electron sharing), usually between non-metals.
- Inorganic compounds often have ionic bonds (electron transfer), usually involving metals and non-metals.
- Not all carbon compounds are organic—exceptions include carbon oxides (CO, CO₂) and carbonates (e.g., CaCO₃).
Carbon’s Atomic Structure and Bonding
- Carbon has six electrons: two in the first shell, four valence electrons in the second shell.
- Four valence electrons allow carbon to form up to four covalent bonds.
- Carbon forms single (one shared pair), double (two shared pairs), or triple bonds (three shared pairs), but not quadruple bonds between carbons.
- The tetrahedral arrangement is typical for carbon with four single bonds.
Structural Representation of Organic Molecules
- Structural formulas, condensed formulas, empirical formulas, and Lewis dot structures represent how atoms are arranged and bonded.
- The empirical formula gives the simplest ratio of atoms (e.g., C₃H₈).
Bonding Capacities of Common Elements
- Carbon: Can form four covalent bonds.
- Nitrogen: Forms three covalent bonds (one lone pair remains).
- Oxygen: Forms two covalent bonds (two lone pairs remain).
- Hydrogen: Forms one covalent bond.
- Halogens (F, Cl, Br, I): Form one covalent bond with three lone pairs.
Unique Properties of Carbon
- Carbon can bond with itself to form chains and rings, enabling millions of different organic compounds.
- Carbon's small presence in Earth's crust makes it vital as the "element of life."
- The diversity of organic compounds is due to carbon’s ability to form various bonds and molecular structures.
Historical Note: Synthesis of Organic Compounds
- Friedrich Wöhler disproved the belief that organic compounds could only come from living things by synthesizing urea from inorganic substances.
Key Terms & Definitions
- Organic compound — a chemical compound containing carbon, often with hydrogen and other elements.
- Covalent bond — a chemical bond where atoms share electron pairs.
- Ionic bond — a bond formed by electron transfer between atoms.
- Valence electrons — electrons in the outermost shell, involved in bonding.
- Lone pair — valence electrons not involved in bonding.
- Empirical formula — the simplest whole-number ratio of atoms in a compound.
Action Items / Next Steps
- Review the bonding capacities of common elements (C, N, O, H, halogens).
- Practice drawing different structural representations of simple organic compounds.