Which of the following molecules can contain a structural isomer?

The correct response relates to the presence of structural isomers, which are compounds that have the same molecular formula but differ in the arrangement of their atoms. Butane (C4H10) and isobutane (also known as methylpropane) are classic examples of structural isomers. They share the same molecular formula, C4H10, yet differ in their structural configuration: butane has a straight-chain structure, while isobutane has a branched structure. This difference in arrangement results in distinct physical and chemical properties, allowing for the classification of these two molecules as structural isomers.

In contrast, the other choices do not present any examples of structural isomers. Oxygen (O2) and hydrogen (H2) are simple diatomic molecules with no possibility for isomerism since they consist of the same kinds of atoms bonded in the same way. Carbon dioxide (CO2) and ethylene (C2H4) have different molecular formulas entirely, meaning they cannot be structural isomers of each other. Lastly, while glucose and ribose are both carbohydrates and share similar functional groups, they are not structural isomers—glucose is a hexose and ribose is a pentose, indicating different molecular formulas (C6