What type of compound is characterized by a carbonyl group at the end of a carbon chain?

The compound characterized by a carbonyl group at the end of a carbon chain is classified as an aldehyde. Aldehydes have the functional group R-CHO, where R represents a hydrocarbon chain or hydrogen, and the carbonyl carbon is bonded to at least one hydrogen atom. This positioning of the carbonyl group at the terminal end of the carbon chain is what distinctly defines aldehydes and differentiates them from other carbonyl-containing compounds.

In contrast, ketones feature a carbonyl group located between two carbon atoms, making them distinct from aldehydes. Alcohols are characterized by the presence of a hydroxyl group (-OH), and ethers consist of an oxygen atom bonded to two alkyl or aryl groups, neither of which involves a carbonyl group. Therefore, the unique structural feature of having the carbonyl group at the end of the carbon chain is what defines aldehydes.