Ketones are chemical compounds that contain a non-terminal carbonyl group (>C=O) as a functional group. Low molecular weight ketones are colorless, mobile liquids and soluble in water due to the polarity of the carbonyl group. They are characterized by a mostly pleasant, fruity smell. Higher molecular weight ketones, on the other hand, are solid substances. | Important ketones include acetone, methyl ethyl ketone (MEK) and cyclohexanone.