Which of the following compounds contains a carbonyl group?

The compound that contains a carbonyl group is an aldehyde. A carbonyl group consists of a carbon atom double-bonded to an oxygen atom (C=O). In the case of aldehydes, this carbonyl group is located at the end of the carbon chain, giving them distinctive properties and reactivity compared to other organic compounds.

Aldehydes can be recognized by their general structure, which includes the functional group RCHO, where R is a hydrocarbon chain or hydrogen. This structure directly indicates the presence of the carbonyl group.

Other options do not contain a carbonyl group. Alkanes consist of single bonds between carbon atoms and lack functional groups altogether. Alkenes contain carbon-to-carbon double bonds but, like alkanes, do not have a carbonyl group. Methane is a simple alkane comprised of one carbon atom and four hydrogen atoms (CH4), which also does not include a carbonyl group.

Thus, the presence of the carbonyl group in aldehydes distinguishes them from other types of hydrocarbons such as alkanes, alkenes, and methane.