A Level Chemistry OCR Practice Exam

What are stereoisomers?

1. Compounds with different structural formulas

2. Compounds with the same structural formula but different arrangements of atoms

3. Molecules that can interconvert easily

4. Isomers that differ by the position of a functional group

The correct answer is: Compounds with the same structural formula but different arrangements of atoms

Stereoisomers are indeed compounds that share the same structural formula but have different arrangements of atoms in three-dimensional space. This concept is crucial in understanding the behavior of molecules, as the spatial arrangement can significantly influence the properties and reactivity of the compounds. Stereoisomerism occurs when molecules have the same connectivity of their atoms (indicated by the structural formula), but the orientation of these atoms in space differs. The two primary categories of stereoisomers are geometric (cis-trans) isomers, which arise from restricted rotation around a bond (often a double bond), and optical isomers (enantiomers), which are non-superimposable mirror images of each other due to the presence of chiral centers. Other choices do not accurately define stereoisomers. For example, compounds with different structural formulas correspond to structural isomers rather than stereoisomers. Additionally, while some molecules can interconvert easily, this does not define stereoisomers specifically, as it depends on the compound in question. Lastly, while the position of a functional group can create different compounds, this also describes another type of isomerism unrelated to stereoisomerism.