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Esters and Esterification

Key Concepts

  • Esters have the general formula :
      O
    ||
     
    R - C - O - R'

    in which R and R' represent alkyl groups.

  • Esters (alkyl alkanoates) are prepared by reacting an alkanol with an alkanoic acid:
    alkanol + alkanoic acid alkyl alkanoate (ester) + water
    R'OH + RCOOH RCOOR' (ester) + H2O

  • Preparation of Esters:
  1. Reflux
    The reaction mixture consisting of the alkanol, the alkanoic acid and a small amount of concentrated sulfuric acid is heated in a vessel with a water-cooled condenser (Liebig condenser) to prevent loss of volatile material.

  2. Separation
    After heating, the reaction mixture is then poured into a separating funnel.
    Calcium carbonate (CaCO3), or a similar neutralizing agent, is added to the mixture to react with any unreacted acid present in the mixture.
    calcium carbonate + acid → water soluble salt + carbon dioxide gas + water

    The less dense organic layer floats on top of the more dense aqueous layer.
    The stop cock on the separating funnel is opened to allow the more dense aqueous layer to be run off, leaving the less dense organic layer containing the ester in the separating funnel.

  3. Purification
    The organic layer separated in the separating funnel above contains the ester. This organic layer is distilled to obtain the pure ester. A sharp boiling point is an indication of the purity of the ester.

Animated Tutorial

Examples of Esters

  • methyl butanoate (apple) :
    methanol + butanoic acid methyl butanoate (ester) + water
    CH3OH + C3H7COOH C3H7COOCH3 (ester) + H2O

  • ethyl methanoate (rum essence) :
    ethanol + methanoic acid ethyl methanoate (ester) + water
    C2H5OH + HCOOH HCOOC2H5 (ester) + H2O

  • ethyl butanoate (pineapple) :
    ethanol + butanoic acid ethyl butanoate (ester) + water
    C2H5OH + C3H7COOH C3H7COOC2H5 (ester) + H2O

  • pentyl ethanoate (banana) :
    pentanol + ethanoic acid pentyl ethanoate (ester) + water
    C5H11OH + CH3COOH CH3COOC5H11 (ester) + H2O

  • pentyl butanoate (apricot) :
    pentanol + butanoic acid pentyl butanoate (ester) + water
    C5H11OH + C3H7COOH C3H7COOC5H11 (ester) + H2O

  • octyl butanoate (orange) :
    octanol + butanoic acid octyl butanoate (ester) + water
    C8H17OH + C3H7COOH C3H7COOC8H17 (ester) + H2O

  • methyl ethanoate (solvent) :
    methanol + ethanoic acid methyl ethanoate (ester) + water
    CH3OH + CH3COOH CH3COOCH3 (ester) + H2O

  • ethyl ethanoate (solvent) :
    ethanol + ethanoic acid ethyl ethanoate (ester) + water
    C2H5OH + CH3COOH CH3COOC2H5 (ester) + H2O
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Related AUS-e-TUTE Topics

Summary of Nomenclature

Naming Straight Chain Alkanes

Naming Branched Chain Alkanes

Naming Simple Alkenes

Naming Simple Alkynes

Naming Structural Isomers of Alkanes

Naming Structural Isomers of Alkenes

Naming Alkanols

Naming Haloalkanes

Carboxylic (alkanoic) Acids

Functional Groups

Combustion of Hydrocarbons

Halogenation of Hydrocarbons

Hydrohalogenation of Hydrocarbons

Hydration of Alkenes

Oxidation of Alkanols

Dehydration of Alkanols (alcohols)

Substitution Reactions of Haloalkanes (alkyl halides)

Preparation and Naming of Polymers (Polymerization)

Properties and Uses of Alkanes

Properties and Uses of Ethene (ethylene)

Properties and Uses of Polythene (polyethylene)

 
 

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