Which of the following has an achiral stereoisomer?
e. 1,3-dibromocyclobutane
f. 2,4-dibromopentane

Verified step by step guidance

1. Step 1: Understand the concept of chirality. A molecule is chiral if it has a non-superimposable mirror image, often due to the presence of a stereocenter (a carbon atom bonded to four different groups). An achiral molecule, on the other hand, either lacks stereocenters or has a plane of symmetry that makes its mirror image superimposable.
2. Step 2: Analyze the structure of 1,3-dibromocyclobutane. Draw the molecule and identify the positions of the bromine atoms on the cyclobutane ring. Check for the presence of stereocenters and determine if the molecule has a plane of symmetry or if it can exist as an achiral stereoisomer.
3. Step 3: Analyze the structure of 2,4-dibromopentane. Draw the molecule and identify the positions of the bromine atoms on the pentane chain. Check for the presence of stereocenters and determine if the molecule has a plane of symmetry or if it can exist as an achiral stereoisomer.
4. Step 4: Compare the findings for both molecules. Determine which molecule has an achiral stereoisomer by identifying if either molecule can adopt a conformation or configuration that results in a plane of symmetry or superimposable mirror images.
5. Step 5: Conclude which molecule (1,3-dibromocyclobutane or 2,4-dibromopentane) has an achiral stereoisomer based on the analysis of their structures and symmetry properties.

Key Concepts

Stereoisomerism

Stereoisomerism refers to the phenomenon where compounds have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of those atoms. This can lead to different properties and reactivities. Stereoisomers can be further classified into enantiomers and diastereomers, depending on their symmetry and the presence of chiral centers.

Chirality

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. A chiral molecule typically has at least one carbon atom bonded to four different substituents, creating two distinct enantiomers. In contrast, achiral molecules possess a plane of symmetry and can be superimposed on their mirror images.

Achiral Stereoisomers

Achiral stereoisomers are stereoisomers that do not exhibit chirality, meaning they can be superimposed on their mirror images. These compounds may still have stereogenic centers but possess a symmetry that negates chirality. Identifying achiral stereoisomers is crucial in organic chemistry, especially when determining the optical activity of a compound.