Which of the following pairs are enantiomers?

Enantiomers are a specific type of stereoisomer that are non-superimposable mirror images of each other, meaning that if you were to place one molecule over the other, they would not match up perfectly despite having the same connectivity of atoms. This feature fundamentally defines enantiomers.

The correct choice identifies molecules that are mirror images of one another, which is the essential criterion for enantiomeric pairs. For example, think of your left and right hands; they are mirror images and cannot be overlaid perfectly on one another, representing a classic example of enantiomers.

While pairs of molecules with differing boiling points, identical chemical characteristics, or the same molecular formula might share some traits or properties, they do not encapsulate the distinct relationship that defines enantiomers. Differing boiling points can occur due to structural differences unrelated to chirality, identical chemical characteristics may apply to diastereomers or other types of isomers, and molecules with the same molecular formula can represent a variety of structural isomers, not all of which will be enantiomers. Thus, the choice that highlights mirror images unequivocally captures the concept of enantiomers.