The reactions of ethanoic acid

1 Solubility and pH

The video shows that ethanoic acid is readily soluble in water due to the effect of hydrogen bonding. Draw a diagram to show the interaction between the two molecules. You should also be able to write down an equation for the reaction with sodium carbonate solution, and explain why ethanoic acid has an acidic nature.

Video - solubility and pH of ethanoic acid

Theory - solubility and pH of ethanoic acid

2 Formation of salts

As ethanoic acid is an acid, it reacts with alkalis to form salts. However, the pH change during this process may appear rather strange. In order to understand it you will need some of the theory of buffer solutions. Watch the video, and try to explain what you see, checking your theory with the link below.

Video - pH changes during salt formation

Theory of pH changes

3 Reaction with phosphorus(V) chloride

We have seen this reagent used before as a test for the OH group in an alcohol. The reaction we observe is very similar, so this is a test for an OH group rather than for an alcohol. Review the reaction of PCl₅ with an alcohol and try to work out the equation for the reaction with ethanoic acid. Check your answer here.

Video - the reaction of phosphorus(V) chloride with an OH group

4 Reaction with alcohols

It is well worth carrying out these reactions in class as it should lead to a number of fruity smelling compounds. I have not shown a video for this reaction as there is little to see, and smelling is rather difficult by video! The reaction is the organic equivalent of salt formation. The reaction produces an organic molecule called an ester and water. Try to write out the equation for the reaction between ethanol and butanoic acid then check your answer using the theory link below.

Ester formation theory