Lecture on Nomenclature: Hydrocarbons and Alcohols

Introduction

• Lecturer: Iman
• Topic: Nomenclature, focusing on hydrocarbons and alcohols

Hydrocarbons

• Hydrocarbons: Compounds with only carbon and hydrogen atoms.
• Alcohols: Compounds with at least one OH group.

Alkanes

• Alkanes: Simple hydrocarbons with formula C_nH_2n+2.
• Single bonds between carbons and hydrogens.
• First four alkanes:
  • Methane: CH₄
  • Ethane: C₂H₆
  • Propane: C₃H₈
  • Butane: C₄H₁₀
• Naming pattern for more than 4 carbons: Greek root + -ane (e.g., Pentane for 5 carbons)
• Recommended: Know the Greek roots for 5 through 12.

Alkenes and Alkynes

• Alkenes: Hydrocarbons with double bonds, suffix -ene.
• Alkynes: Hydrocarbons with triple bonds, suffix -yne.
• Naming rule: Double/triple bonds are given the lowest possible number.
  • Example: Two-pentene (double bond at 2nd carbon).
  • For multiple double bonds: E.g., 2,4-pentadiene (double bonds at 2nd and 4th carbons).

Alcohols

• Definition: Contain a hydroxyl group (OH).
• Naming: Replace -e with -ol (ethane → ethanol).
• Priority: Hydroxyl groups take priority over double and triple bonds.
  • Example: 5-methyl-2-heptanol (OH group at 2nd position, methyl group at 5th position).
• Dials: Two hydroxyl groups, termed geminal (same carbon) or vicinal (adjacent carbons).

Aldehydes and Ketones

• Aldehydes: Terminal carbonyl group, replace -e with -al (e.g., butanal).
  • Common names: Methanal (formaldehyde), Ethanal (acetaldehyde), Propanal (proprionaldehyde)
• Ketones: Carbonyl group within the carbon chain, replace -e with -one (e.g., 3-hexanone)
  • Ketone takes priority over double/triple bonds
  • Substituent name: Prefix oxo-

Carboxylic Acids and Derivatives

• Carboxylic Acids: Carbonyl group with a hydroxyl group, high priority.
  • Naming: Replace -e with -oic acid (ethane → ethanoic acid).
  • Common names: Methanoic acid (formic acid), Ethanoic acid (acetic acid).
• Esters: Carboxylic acid derivatives with -OR group.
  • Naming: Alkyl name + parent acid with -oate (e.g., methyl butanoate).
• Amides: Carboxylic acid derivatives with -NH₂ group.
  • Naming: Name substituents attached to nitrogen first with prefix N- (e.g., N,N-dimethyl ethanamide).
• Anhydrides: Formed from two carboxylic acid molecules by removing water.
  • Naming: Parent acid + anhydride (e.g., ethanoic anhydride).
  • If asymmetric: Name both acids (e.g., ethanoic propanoic anhydride).

Priority and Summary

• Functional Group Priority: carboxylic acids > anhydrides > esters > amides > aldehydes > ketones > alcohols > alkenes > alkynes > alkanes.
• Suffix vs. Prefix: Use suffix if functional group has highest priority; otherwise, use prefix.
• Familiarize with common and IUPAC names for key functional groups.

Next Steps

• Practice problems
• Engage with questions or comments for further clarification