The carboxylic acid functional group is the highest priority functional group. The -COOH functional group can also be seen here molecularly:

When naming a group with a carboxylic functional group, you take the alkane name (for instance, butane), and drop the -ane and add -oic acid. So, butane would be butanoic acid. So name this compound:

This would be butanoic acid. Pretty easy. Try this one:

This is benzoic acid! See, carboxylic acids are pretty easy.

Historical Names

The hardest thing about acids is that a lot of them have "historic" names which have pattern. So here are some of them:

Structure	IUPAC Name	Historical Name
	Methanoic Acid	Formic Acid
	Ethanoic Acid	Acetic Acid
	Propanoic Acid	Propionic Acid
	Butanoic Acid	Butyric Acid