Organic Chemistry - Alcohols, Carboxylic Acids and Esters

This section covers alcohols, carboxylic acids, and esters as homologous series, their structures, naming, reactions, formation methods, and applications, including esterification and uses in industry.

1. Alcohols
  • 🔹 Functional Group:

    🔹 Hydroxyl group (–OH).

  • 🔹 General Formula:

    🔹 CₙH₂ₙ₊₁OH

  • 🔹 Physical Properties:
    • 🔹 Polar due to –OH group, short chains soluble in water
    • 🔹 Higher boiling points than hydrocarbons of similar mass
  • 🔹 Uses:
    • 🔹 Solvents
    • 🔹 Fuels
    • 🔹 Intermediates in synthesis
  • 🔹 Structures & Naming (C₁–C₄):
    • 🔹 Unbranched:
      • 🔹 Methanol
      • 🔹 Ethanol
      • 🔹 Propan-1-ol
      • 🔹 Propan-2-ol
      • 🔹 Butan-1-ol
      • 🔹 Butan-2-ol
    • 🔹 Branched Example:

      🔹 2-methylpropan-1-ol

  • 🔹 Reactions:
    • 🔹 Combustion:

      🔹 Alcohol + O₂ → CO₂ + H₂O (releases heat)

    • 🔹 Oxidation to Carboxylic Acids:

      🔹 Ethanol → Ethanoic acid using acidified potassium manganate(VII) or potassium dichromate(VI)

  • 🔹 Formation:
    • 🔹 Catalytic Addition of Steam to Ethene:
      • 🔹 Reaction:

        🔹 CH₂=CH₂ + H₂O → C₂H₅OH

      • 🔹 Conditions:

        🔹 300°C, 60 atm, phosphoric acid catalyst

      • 🔹 Advantages:

        🔹 Fast, pure product

      • 🔹 Disadvantage:

        🔹 Requires fossil fuel ethene

    • 🔹 Fermentation of Sugars:
      • 🔹 Reaction:

        🔹 C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂

      • 🔹 Conditions:

        🔹 30–40°C, yeast, anaerobic

      • 🔹 Advantages:

        🔹 Renewable

      • 🔹 Disadvantage:

        🔹 Slower, impure product

2. Carboxylic Acids
  • 🔹 Functional Group:

    🔹 Carboxyl group (–COOH)

  • 🔹 General Formula:

    🔹 CₙH₂ₙ₊₁COOH

  • 🔹 Properties:

    🔹 Weak acids; partially ionise in water

  • 🔹 Structures & Naming (C₁–C₄):
    • 🔹 Methanoic acid
    • 🔹 Ethanoic acid
    • 🔹 Propanoic acid
    • 🔹 Butanoic acid
  • 🔹 Reactions:
    • 🔹 With Carbonates:

      🔹 Produces salt, water, and CO₂ (effervescence). Example: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂

    • 🔹 With Bases:

      🔹 Produces salt and water. Example: CH₃COOH + NaOH → CH₃COONa + H₂O

    • 🔹 With Metals:

      🔹 Produces salt and hydrogen gas. Example: 2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂

  • 🔹 Formation:
    • 🔹 Oxidation of Ethanol:

      🔹 CH₃CH₂OH → CH₃COOH using acidified potassium manganate(VII) or potassium dichromate(VI)

3. Esters
  • 🔹 Formation:

    🔹 Carboxylic acid + Alcohol ⇌ Ester + Water

  • 🔹 Conditions:

    🔹 Heat with concentrated sulphuric acid (catalyst)

  • 🔹 Properties:

    🔹 Sweet-smelling liquids, used in perfumes and flavourings

  • 🔹 Naming & Formulae (C₁–C₄):
    • 🔹 Rule:

      🔹 Alcohol part (–yl) + Acid part (–oate)

    • 🔹 Examples:
      • 🔹 Methanol + Ethanoic acid → Methyl ethanoate (CH₃COOCH₃)
      • 🔹 Ethanol + Propanoic acid → Ethyl propanoate (C₂H₅COOC₂H₅)
      • 🔹 Propanol + Methanoic acid → Propyl methanoate (HCOOC₃H₇)
      • 🔹 Butanol + Butanoic acid → Butyl butanoate (C₃H₇COOC₄H₉)

  • 🔹 Combustion of ethanol: C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
  • 🔹 Oxidation of primary alcohol to carboxylic acid: CH₃CH₂OH + [O] → CH₃COOH + H₂O
  • 🔹 Reaction of carboxylic acid with carbonate: 2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
  • 🔹 Reaction of carboxylic acid with base: CH₃COOH + NaOH → CH₃COONa + H₂O
  • 🔹 Reaction of carboxylic acid with metal: 2CH₃COOH + Mg → (CH₃COO)₂Mg + H₂
  • 🔹 Esterification (carboxylic acid + alcohol): CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O (conc. H₂SO₄ as catalyst)
  • 🔹 Fermentation of glucose to ethanol: C₆H₁₂O₆ → 2 C₂H₅OH + 2 CO₂

  • ⚠️ All alcohols are highly soluble in water regardless of chain length.
  • ⚠️ Carboxylic acids are strong acids like HCl.
  • ⚠️ Esters are naturally occurring and cannot be synthesized.
  • ⚠️ Oxidation of alcohols always produces carboxylic acids; aldehydes are ignored.

  • 👉 Memorize functional groups and general formulas for alcohols and carboxylic acids.
  • 👉 Practice naming branched and unbranched alcohols and esters.
  • 👉 Understand both industrial and fermentation methods of ethanol production, including pros and cons.
  • 👉 Learn reactions of carboxylic acids with carbonates, bases, and metals with example equations.
  • 👉 Know the esterification reaction, catalyst, and naming rules clearly.

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