Skip to main content
Ch. 4 - Isomers: The Arrangement of Atoms in Space
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 5, Problem 49a,b

Which of the following compounds has a stereoisomer that is a meso compound?
a. 2,4-dibromohexane
b. 2,4-dibromopentane

Verified step by step guidance
1
Identify the structural features required for a compound to have a meso stereoisomer. A meso compound must have: (1) at least two stereocenters, (2) an internal plane of symmetry, and (3) be optically inactive despite having stereocenters.
Draw the structures of 2,4-dibromohexane and 2,4-dibromopentane. Place the bromine atoms at the 2nd and 4th carbon positions in each compound, ensuring you consider all possible stereoisomers (R and S configurations at each stereocenter).
Examine the stereoisomers of 2,4-dibromohexane. Check if any of the stereoisomers have an internal plane of symmetry. For example, if the 2nd carbon is R and the 4th carbon is S (or vice versa), the molecule may exhibit symmetry.
Repeat the same analysis for 2,4-dibromopentane. Draw all possible stereoisomers and check for the presence of an internal plane of symmetry in any of them.
Determine which compound (if any) has a stereoisomer that meets the criteria for being a meso compound. This will involve identifying the compound with a stereoisomer that is optically inactive due to symmetry.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
3m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

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 physical and chemical properties. Stereoisomers can be further classified into enantiomers and diastereomers, with the former being non-superimposable mirror images and the latter not being mirror images.
Recommended video:
Guided course
01:58
Determining when molecules are stereoisomers.

Meso Compounds

Meso compounds are a specific type of stereoisomer that possess multiple chiral centers but are achiral due to an internal plane of symmetry. This means that despite having chiral centers, the overall molecule does not exhibit optical activity. Meso compounds can often be identified by their symmetrical structure, which allows for superimposition on their mirror images.
Recommended video:
Guided course
04:10
The 3 rules of meso compounds.

Chirality and Chiral Centers

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, typically due to the presence of chiral centers, which are carbon atoms bonded to four different substituents. The presence of chiral centers in a molecule can lead to the formation of stereoisomers. Understanding chirality is crucial for determining the optical activity and potential stereoisomers of a compound.
Recommended video:
Guided course
05:10
What is chirality?