What is the minimum number of carbon atoms required in an acyclic ketone to exhibit metamerism? — Isomerism and Stereochemistry Chemistry Question

💡 Solution & Explanation

Metamerism requires different alkyl groups attached to the polyvalent functional group ($-CO-$). The smallest ketone, propanone ($C_3$), has only one arrangement ($CH_3-CO-CH_3$). Butanone ($C_4$) also has only one arrangement ($CH_3-CO-CH_2CH_3$). A ketone with 5 carbons can be 3-pentanone ($CH_3CH_2-CO-CH_2CH_3$) or 2-pentanone ($CH_3-CO-CH_2CH_2CH_3$), which are metamers. Thus, 5 carbons are required.