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*Revision Materials* 1 Atomic Structure 2 Atoms, molecules and stoichiometry 3 Chemical Bonding 4 States of matter 5 Chemical energetics 6 Electrochemistry 7 Equilibria 8 Reaction kinetics 9 The Periodic Table, chemical periodicity 10 Group 2 11 Group 17 12 Nitrogen and sulfur 13 Organic 14 Hydrocarbons 15 Halogen compounds 16 Hydroxy compounds 17 Carbonyl compounds 18 Carboxylic acids and derivatives 19 Nitrogen compounds 20 Polymerisation 21 Organic synthesis 22 Analytical techniques 23 Chemical energetics 24 Electrochemistry 25 Equilibria 26 Reaction kinetics 27 Group 2 28 Chemistry of transition elements 29 Organic 30 Hydrocarbons 31 Halogen compounds 32 Hydroxy compounds 33 Carboxylic acids and derivatives 34 Nitrogen compounds 35 Polymerisation 36 Organic synthesis 37 Analytical techniques

18 Carboxylic acids and derivatives

18.1 Carboxylic acids 18.2 Esters

Esters

Specification Reference Organic Chemistry, Carboxylic acids and derivatives 18.2

Quick Notes

  • Esters are formed in a condensation reaction between an alcohol and a carboxylic acid using concentrated H2SO4 as a catalyst.
  • This reaction is called esterification and is reversible.
  • Hydrolysis of esters splits them back into an alcohol and acid (or salt):
    • Acid hydrolysis: ester + water ⇌ acid + alcohol
    • Alkaline hydrolysis: ester + OH− → salt + alcohol (not reversible)

Full Notes

Esters and their reactions have been outlined in more detail here
This page is just what you need to know for CIE A-level Chemistry :)

Esters are compounds that contain the COOR functional group. They are generally volatile (easily vapourise) and have sweet, fruity smells.

Preparation of Esters (Esterification)

Carboxylic acids react with alcohols in the presence of an acid catalyst (H2SO4) to form esters in condensation reactions (water is released).

CIE A-Level Chemistry diagram showing esterification reaction between a carboxylic acid and alcohol forming an ester and water.

Hydrolysis of Esters

Esters can be broken apart in hydrolysis reactions. The products obtained depend on the conditions used.

Acid Hydrolysis:

CIE A-Level Chemistry diagram showing ester undergoing hydrolysis with dilute acid to form a carboxylic acid and alcohol.

Alkaline Hydrolysis:

CIE A-Level Chemistry diagram showing ester undergoing alkaline hydrolysis with NaOH to form a carboxylate salt and alcohol.
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Matt’s Exam Tip

Remember the hydrolysis of an ester in acidic conditions is reversible (just like the formation of an ester from a carboxylic acid and alcohol) whereas the hydrolysis of an ester in alkaline conditions isn’t reversible.

Summary