What is the structural formula for 2-butene?

The structural formula for 2-butene is represented correctly as CH₃-CH=CH-CH₃. This compound is classified as an alkene, which means it contains at least one carbon-carbon double bond. In the case of 2-butene, the double bond is located between the second and third carbon atoms in the four-carbon chain, hence the name "2-butene."

To elaborate, the carbon chain consists of four carbon atoms (C₄), and the molecular formula for 2-butene is C₄H₈, indicating that there are eight hydrogen atoms corresponding to the four carbon atoms, which is typical for alkenes due to the presence of the double bond reducing the number of hydrogen atoms by two compared to the corresponding alkane.

Moreover, the positioning of the double bond impacts the isomerism of the compound. 2-butene can exist in two geometric forms, cis and trans, depending on the arrangement of the substituents around the double bond. This aspect underscores the importance of providing the correct structures in organic nomenclature to convey accurate information about the substance's properties and reactivity.

The other choices do not accurately reflect the structure of 2-butene. For instance, CH₂