Esters – The Fragrant Compounds

📚 Key Concepts

🔹 Real-Life Example

The sweet smell of ripe fruits like bananas, apples, and pineapples comes from esters. The fruity flavoring in candies and the pleasant fragrance in perfumes are also due to esters. Even nail polish remover contains ethyl acetate, an ester!

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Esters: Organic compounds formed by the reaction between carboxylic acids and alcohols, with the elimination of water. They have the functional group -COO-.

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🧪 Formation and Properties

🔸 Esterification Reaction

General Reaction: RCOOH + R’OH ⇌ RCOOR’ + H₂O (Acid + Alcohol ⇌ Ester + Water)

Example: CH₃COOH + C₂H₅OH ⇌ CH₃COOC₂H₅ + H₂O (Acetic acid + Ethanol ⇌ Ethyl acetate + Water)

Conditions:

  • Concentrated H₂SO₄ as catalyst
  • Heating required
  • Reversible reaction

🔸 Properties of Esters

  • Pleasant smell: Most esters have fruity odors
  • Lower boiling points: Than corresponding acids and alcohols
  • Immiscible with water: Generally insoluble
  • Neutral compounds: Neither acidic nor basic

🔸 Saponification

Ester + Base → Salt + Alcohol

CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH

This reaction is used in soap making from fats and oils.

🧪 Uses of Esters

  • Artificial flavoring: Food industry
  • Perfumes: Fragrance industry
  • Solvents: Nail polish remover, paints
  • Plasticizers: Making plastics flexible
  • Soap making: Saponification of fats
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🔍 Advanced: Natural vs Artificial Flavors

Natural fruit flavors are complex mixtures of many esters, while artificial flavors often use single esters that mimic the dominant smell compound.