IBDP Chemistry: Carbonxylic Acid Derivatives

• A compound that can be hydrolysed from the parent carboxylic acid
• Have a common sequence of atoms in their structure- acyl group (homologous series)

• Named from the parent carboxylic acid from which it is derived, remove ‘-oic acid’ and replace with ‘-oate’
• The alkyl chain attached to the oxygen of the COO group is then added as the first word in the name e.g. methyl, ethyl, propyl etc. – this comes from the alcohol e.g. methanol - methyl

Esterification

• Alcohol + carboxylic acid --> ester + water
• Alcohol warmed with a carboxylic acid
• Concentrated sulfuric acid catalyst
• e.g. propanoic acid + ethanol --> ethyl propanoate + water
  C2H5COOH + C2H5OH --> C2H5COOC2H5 + H2O

1. Pour 2cm of ethanol and 2cm of propanoic acid into a boiling tube
2. Carefully add a few drops of concentrated sulfuric acid to the mixture
3. Place the boiling tube in a beaker of hot water, approx. 80°C
4. Leave the boiling tube in the water for about 5 minutes
5. Pour the contents of the boiling tube into a beaker containing aqueous sodium carbonate – this removes the smell of any carboxylic acid that has not reacted- easier to detect the smell of the ester (oily drops of the ester floating on the water- smell aroma of ester)

• Ester heated under reflux with dilute aqueous acid
• Add H2O and dilute hydrochloric acid. The ester is broken down by water, whilst the acid acts as a catalyst
• Produces a carboxylic acid and an alcohol (reverse of esterification)
• e.g. methyl 2-hydroxy benzoate + water --> 2-hydroxy benzoic acid + methanol

• Ester heated under reflux with aqueous hydroxide ions (OH-)
• Produces a carboxylate ion (salt) and an alcohol
• Saponification – the salt can be used to make a soap

Ester + aqueous alkali (e.g NaOH or KOH) --> salt + alcohol

• e.g. methyl ethanoate + KOH --> sodium ethanoate + methanol

• Many food flavourings, often mixtures of esters are used
• Many perfumes contain mixtures of esters in a solvent that quickly evaporates e.g. ethanol
• Esters are often used as solvents e.g. ethyl ethanoate is used in nail varnish
• Esters can be used as plasticisers- these are added to polymers to make them more flexiible

This is the end of this topic.