Why?

* Isomers are molecules with the same molecular formula but different structural arrangements.

* Acetic acid has a very simple structure, with a single carbon chain and a carboxylic acid functional group.

* There are no other ways to arrange the atoms in acetic acid to create a different molecule with the same formula.

However, there are two functional isomers of acetic acid, which are:

* Methyl formate (HCOOCH3): This has the same molecular formula (C2H4O2) as acetic acid but has a different functional group - an ester instead of a carboxylic acid.

* Glycolaldehyde (HOCH2CHO): This also has the same molecular formula (C2H4O2) but has an aldehyde functional group and a hydroxyl group.

Therefore, while acetic acid doesn't have structural isomers, it does have functional isomers.