3.9 Carboxylic acids and esters

Question 1

Does a carboxylic acid dissolve in water

Answer 1

The COOH group is very soluble in water due to hydrogen bonding, but the hydrocarbon chain of a carboxylic acid is non-polar, so doesn’t dissolve in water.
Whether a carboxylic acid is soluble depends on the length of the carbon chain
Shorter carboxylic acids will dissolve easier because chain is short

Question 2

How are esters formed

Answer 2

formed by reacting carboxylic acid with an alcohol
conc H2SO4 catalyst needed
reaction is reversible
ethanoic acid + butan-1-ol –><– butylethanoate + H2O

Question 3

Define hydrolysis

Answer 3

breaking a bond using water

Question 4

How can an ester by hydrolysed back into its constitutent elements
use propylethanoate as an example

Answer 4

1) acid catalysed hydrolysis
propylethanoate + H2O –><– ethanoic acid + propan-1-ol
2) Base catalysed hydrolysis
same reaction, NaOH instead of H^+ as the catalyst
However NaOH could further react with ethanoic acid

Question 5

Name some uses of esters

Answer 5

• solvents
• plasticisers
• vegetable oil