The functional group of the ketones is -CO-. The carbon atom is double bonded to the oxygen. The groups connected to the remaining bonds are alkyl or aryl groups (not hydrogen, which would result in the formation of an aldehyde). The alkyl or aryl groups modify the behaviour of the ketone in the normal way; for example as the molecular mass increases the boiling point of the resultant ketone increases. One of the most common ketones is acetone.

The functional group is prepared in one of two ways, either by partial chemical oxidation of a secondary alcohol or by dehydrogenation, with heat and a catalyst, of a secondary alcohol. Both of these processes remove the hydrogen from the hydroxyl group and allow a double bond to form between the connecting carbon and the oxygen.

The majority of reactions in which the ketone functional group...