Which of the following is NOT considered a ketone?

Acetic acid is a carboxylic acid, not a ketone. The defining feature of a ketone is the presence of a carbonyl group (C=O) flanked by two carbon atoms, making it structurally distinct from other types of organic compounds. In the case of acetic acid, it has a carbonyl group (C=O), but it is bonded to a hydroxyl group (−OH), which characterizes carboxylic acids rather than ketones.

On the other hand, methyl isobutyl ketone, methyl ethyl ketone, and diacetone alcohol all contain the carbonyl group connected to carbon atoms, thus classifying them as ketones. Understanding these structural differences is crucial for accurately identifying organic compounds in various chemical contexts, such as in paint formulations or solvent applications in the painting industry.