JAMB Chemistry 2023 Paper

Concept:Alkanals are the same as aldehydes, and their functional group is the carbonyl group.Explanation:An alkanal always contains a carbonyl group, written as $\mathrm{C=O}$.This carbonyl group is a carbon atom double-bonded to an oxygen atom.In an alkanal, the carbonyl carbon is also bonded to at least one hydrogen atom, so the structure is $\mathrm{R-CHO}$.The hydroxyl group $-\mathrm{OH}$ belongs to alcohols, not alkanals.The alkyl group $-\mathrm{R}$ is just a hydrocarbon branch, not a functional group.The carboxyl group $-\mathrm{COOH}$ is found in alkanoic acids, not alkanals.Therefore, the functional group that identifies an alkanal is the carbonyl group.Answer:A. Carbonyl group ($\mathrm{C=O}$)