Lecture Notes: IUPAC Nomenclature and Organic Chemistry

Introduction

• IUPAC: International Union of Pure and Applied Chemists
  • Perceived as making chemistry challenging, but aims to standardize chemical naming.
  • Ensures clarity and consistency in chemical nomenclature.

Importance of IUPAC Naming

• Translates names into chemical structures.
• Names relate to the actual chemical reality, enabling universal understanding.

Basic Steps in Chemical Nomenclature

Step 1: Determine Carbon Chain Length

• Prefixes based on carbon count:
  • Meth-: 1 carbon
  • Prop-: 3 carbons
  • Pent-: 5 carbons
  • Tricosa-: 23 carbons (example of complex naming)
• Identify the longest carbon chain first.

Step 2: Determine Suffix

• Suffixes depend on bonds or functional groups:
  • Single, double, or triple bonds: propane, propene, propyne.
  • Functional groups add specific suffixes:
    • Alcohols: -ol, e.g., ethanol
    • Aldehydes: -al, e.g., ethanal
    • Ketones: -one, e.g., hexanone
    • Amines: -amine, e.g., ethanamine
    • Carboxylic acids: -oic acid, e.g., ethanoic acid

Step 3: Parent Functional Group

• Determines the main suffix.
• Precedence list by IUPAC defines which group is prioritized.
• Carboxylic acid often dominates the nomenclature.

Step 4: Identify Side Chains and Additional Groups

• Name and number any additional groups or side chains.
• Use numbers to specify locations on the chain (lowest possible numbers preferred).

Example: Angelic Acid

• Angelic Acid: Common name derived from a flower.
• Systematic Name: 2-methylbut-2-enoic acid
  • Carbon Count: Four carbons (butene derivative).
  • Groups: Methyl group on second carbon, carboxylic acid.
  • Correct numbering ensures clarity in the structure.

Cis/Trans Designation

• Important for identifying double bond orientations.
• Example used: cinnamaldehyde as trans-3-phenylprop-2-enal.

Conclusion

• IUPAC provides a standard language for chemistry, ensuring precise communication.
• Nomenclature can be complex but avoids ambiguity in chemical structures.
• Resources are available for complex naming beyond simple memorization.
• The goal is to understand why systematic naming is advantageous.

Acknowledgments

• Written by Hank Green.
• Chemistry consultant: Dr. Heiko Langner.
• Production team details included in the transcript.