Which of the following represents the molecular structure of 2-butanone?

2-butanone, also known as methyl ethyl ketone (MEK), has a specific molecular structure that corresponds to a ketone functional group located in the middle of a four-carbon chain. The correct representation of 2-butanone must show the carbonyl group (C=O) positioned between two other carbon atoms, ensuring that the overall chain contains four carbon atoms in total.

In the structure represented by the correct choice, you can observe that there is a carbonyl group (C=O) bonded to two carbon atoms, which can be confirmed as a ketone since it is sandwiched between two alkyl groups (in this case, ethyl and methyl). The formula correctly displays a total of four carbon atoms (C4) and a carbonyl group, matching the definition of 2-butanone.

The other representations do not accurately depict the structure of 2-butanone. For instance, others might either place the carbonyl group at an incorrect position in the carbon chain or present the wrong total number of carbon atoms, distinguishing them from the correct structure of 2-butanone. Hence, the accuracy of the observed molecular structure is vital in determining the correct answer.