The compound has four carbons in a chain with a double-bonded oxygen on the terminal carbon. This makes it an aldehyde, specifically butanal.
Step 2: Compound 11
The compound has a carboxylic acid functional group. Because it only has one carbon, it is formic acid or methanoic acid.
Step 3: Compound 12
The compound has a ketone functional group (internal C=O). The longest chain has three carbons, making it a propanone. It is also called acetone or dimethyl ketone.