Lecture on Nomenclature: Hydrocarbons and Alcohols

Introduction

• Lecture continuation on nomenclature.
• Focus on hydrocarbons and alcohols.

Hydrocarbons

• Definition: Compounds containing only carbon and hydrogen.
• Types:
  • Alkanes: Simplest form with formula $C_nH_{2n+2}$.
    • Naming based on number of carbons.
    • Examples:
      • Methane: 1 carbon
      • Ethane: 2 carbons
      • Propane: 3 carbons
      • Butane: 4 carbons
    • Naming Rule: For more than four carbons, use Greek root + 'ane'.
      • Pentane: 5 carbons
      • Hexane: 6 carbons
  • Alkenes: Have at least one double bond.
    • Suffix: 'ene'
    • Example: Pentene (five carbons, double bond at position 2)
    • Naming: Numbering double bond with lower carbon number (e.g., 2-pentene).
  • Alkynes: Have at least one triple bond.
    • Suffix: 'yne'
    • Naming similar to alkenes, using lower carbon numbers for triple bonds.

Alcohols

• Definition: Hydrocarbons containing at least one hydroxyl group (OH).
• Naming: Replace 'e' in alkane with 'ol'.
  • Example: Ethanol (two carbons and an OH group), 2-heptanol
• Priority: Hydroxyl group has higher priority over double/triple bonds.
• Special Cases: If not highest priority, use prefix 'hydroxy'.

Aldehydes and Ketones

• Definition: Contain a carbonyl group (carbon double-bonded to oxygen).
• Aldehydes:
  • Terminal functional groups.
  • Named by replacing the 'e' of parent alkane with 'al'.
  • Common names:
    • Methanal: Formaldehyde
    • Ethanal: Acetaldehyde
• Ketones:
  • Carbonyl group in the middle of carbon chain.
  • Replace 'e' in alkane with 'one'.
  • Example: 3-hexanone

Carboxylic Acids and Derivatives

• Carboxylic Acids:
  • Have carbonyl and hydroxyl group on terminal carbon.
  • Highest priority functional group.
  • Named by replacing 'e' with 'oic acid'.
  • Common names:
    • Methanoic: Formic acid
    • Ethanoic: Acetic acid
• Esters:
  • Replace 'OH' with 'OR'.
  • Naming: Alkyl name of esterifying group + parent acid with 'oate'.
  • Example: Ethyl propanoate
• Amides:
  • Replace 'OH' with amino group.
  • Named like esters but suffix becomes 'amide'.
  • Example: N,N-dimethyl ethanamide
• Anhydrides:
  • Formed by removal of water from two carboxylic acids.
  • Named by replacing 'acid' with 'anhydride'.
  • Example: Ethanoic anhydride

Functional Group Priority

• Highest priority to lowest:
  1. Carboxylic acids
  2. Anhydrides
  3. Esters
  4. Amides
  5. Aldehydes
  6. Ketones
  7. Alcohols
  8. Alkenes/Alkynes
  9. Alkanes

Conclusion

• Summary of nomenclature rules for various functional groups.
• Next lecture will include practice problems.
• Encourage questions and comments.