Advanced Placement (AP) Biology Practice Exam

What characterizes geometric isomers?

1. Different covalent arrangements of atoms

2. Identical structural formulas but different spatial orientations

3. Identical physical properties

4. Mirror image structures

The correct answer is: Identical structural formulas but different spatial orientations

Geometric isomers are characterized by having identical structural formulas but differing in the spatial orientation of their atoms or groups around a double bond or a ring structure. This variation arises due to the limitations in rotation around double bonds, which prevents certain atoms or groups from freely rotating into different positions. As a result, geometric isomers can exist in different forms, typically referred to as cis and trans configurations, where specific groups maintain different relative positions to one another. While different covalent arrangements might pertain to structural isomers, geometric isomers maintain the same connectivity of their atoms. They also tend to exhibit differences in physical properties due to their distinct spatial arrangements, which is not consistent with the characteristic of having identical physical properties. Lastly, mirror image structures refer to enantiomers, not geometric isomers, which further distinguishes their characteristics.