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VIDEO: CH. 20 Defining Organic Chemistry

Jun 11, 2025

Overview

This lecture introduces the foundational concepts of organic chemistry, highlighting the role of carbon in biological molecules and distinguishing organic from inorganic compounds.

Course Structure & Pre-Lecture Tasks

  • Each class session is divided into pre-lecture, lecture, and post-lecture activities.
  • Pre-lecture tasks include concept maps, reviewing previous material, and completing practice problems to prepare for new content.

Importance of Organic Chemistry

  • Organic chemistry studies compounds that are central to life and many materials (DNA, proteins, plastics, drugs).
  • Carbon-based compounds are essential for living organisms, while silicon-based compounds make up much of the Earth's geology.

Elements and Their Roles

  • The Earth's major realms (sea, atmosphere, land, living organisms) are characterized by different abundant elements.
  • Silicon forms the backbone of geological structures through silicon-oxygen bridges (e.g., silica, silicates).
  • Carbon forms the basis of biological structures due to its ability to bond to itself and other non-metals.

Unique Properties of Carbon

  • Carbon can catenate (bond to itself), forming stable chains, rings, and branches.
  • Carbon’s bonding versatility allows for millions of organic compounds, including biomolecules like DNA, proteins, carbohydrates, and lipids.
  • Organic compounds must have at least one carbon-hydrogen bond.

Biomolecules and Their Structures

  • Biomolecules—nucleic acids, proteins, lipids, carbohydrates—are made up of carbon-based chains or rings.
  • Biomolecules feature carbon bonded to hydrogen, oxygen, nitrogen, sulfur, and sometimes halogens.
  • Skeletal structures are a simplified way to represent carbon bonding in molecules.

Monomers and Polymers

  • Monomers are single units; polymers are chains of repeated monomers.
  • Organic compounds can be modular, forming complex structures from simple repeating units.

Defining Organic Chemistry

  • Organic chemistry is the study of compounds primarily composed of carbon and hydrogen, often with oxygen, nitrogen, sulfur, or halogens.

Key Terms & Definitions

  • Organic Compound — A molecule containing at least one carbon-hydrogen bond.
  • Catenation — The ability of an element (like carbon) to form chains or rings by bonding to itself.
  • Biomolecule — Molecule essential for life, including DNA, proteins, carbohydrates, and lipids.
  • Monomer — A single molecular unit that can join others to form polymers.
  • Polymer — A large molecule made from repeating monomer units.
  • Skeletal Structure — A simplified representation of organic molecules showing carbon-to-carbon bonds.

Action Items / Next Steps

  • Complete the pre-lecture concept map and review previous material.
  • Create a flashcard with your own definition of organic chemistry.
  • Prepare questions about the role of carbon in life and the difference between organic and inorganic chemistry.