The first and second members, respectively, of the ketone homologous series are:

The first and second members of the ketone homologous series are propanone (commonly known as acetone) and butanone (methyl ethyl ketone). Ketones have the general formula CnH2nO and are characterized by a carbonyl group (C=O) bonded to two carbon atoms. These compounds are commonly used as solvents in various industries.