M5

• Alcohols


  Compounds containing hydroxyl group (OH) connected to an aliphatic hydrocarbon
• Classification of alcohols

  • Primary
  • Secondary
  • Tertiary
• Alcohols may be classified as


  • Containing one hydroxyl group
  • Containing two hydroxyl groups
  • Containing three hydroxyl groups
  • Containing many hydroxyl groups
• Solubility of alcohols in water

  • Longer alkyl group disrupt hydrogen bonding among the water molecules leading to water insolubility
  • Solubility increases with branching because the surface area of the hydrocarbon part decreases with branching
• Solubilities of alcohols in water

  • Methanol: Infinitely soluble
  • Ethanol: Infinitely soluble
  • Propanol: Infinitely soluble
  • Butanol: 9 g/100g
  • Pentanol: 2.7 g/100g
  • Hexanol: 0.6 g/100g
  • Heptanol: 0.18 g/100g
  • Octanol: 0.054 g/100g
  • Decanol: Insoluble in water
• Boiling point of alcohols

  • Alcohols have higher boiling point than corresponding alkanes
  • Branching decreases the boiling point
• Acidity of alcohols

  • Increase in alkyl groups decreases acidity (primary =most acidic, tertiary =least acidic)
• Lucas test


  Used to distinguish among primary, secondary, and tertiary water-soluble alcohols
• Lucas reagent


  • Zinc chloride in concentrated sulfuric acid
  • Positive result: Turbid solution or white precipitate