ketone (kēˈtōn) [key], any of a class of organic compounds that contain the carbonyl group, C&eq;O, and in which the carbonyl group is bonded only to carbon atoms. The general formula for a ketone is RCOR′, where R and R′ are alkyl or aryl groups. The simplest ketone, where R and R′ are methyl groups, is acetone; this is one of the most important ketones used in industry. Low-molecular-weight ketones are used chiefly as solvents. Ketones may be prepared by several methods, including the oxidation of secondary alcohols and the destructive distillation of certain salts of organic acids. Ketones are related to the aldehydes but are less active chemically.