Final answer:
The terms enantiomers, diastereomers, or the same compound relate to the spatial arrangement of atoms in stereoisomers. Enantiomers are non-superimposable mirror images, while diastereomers are stereoisomers that are not mirror images and have different properties.
Step-by-step explanation:
The subject of this question is organic chemistry, focusing on the concepts of stereoisomerism. In terms of determining whether enantiomers, diastereomers, or if they are the same compound describes a pair of compounds, one has to consider the spatial arrangement of atoms within the molecules.
Enantiomers are stereoisomers that are non-superimposable mirror images of each other. This means that enantiomers have a chiral center with atoms or groups arranged in such a way that the molecules are mirror images but cannot be aligned perfectly on top of one another. For example, D and L sugars are enantiomers because they have identical molecular formulas and the same atom connectivity but differ in the orientation of atoms around the chiral center, causing them to deflect polarized light in opposite directions.
Diastereomers, on the other hand, are stereoisomers that are not mirror images of each other and are not superimposable. They have different physical and chemical properties. An example of diastereomeric relationship can be observed in D-erythrose and D-threose, as well as L-erythrose and L-threose, where these pairs of sugars share the same molecular formula but differ in the configuration of their chiral centers.