Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

5. Chirality

Constitutional Isomers vs. Stereoisomers

Organic Chemistry

5. Chirality

Constitutional Isomers vs. Stereoisomers

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Problem 66d

Textbook Question

How many stereoisomers are possible for the following alkenes?
(d)

Verified step by step guidance

Step 1: Analyze the structure of the given alkene. The molecule consists of a cyclohexene ring with a double bond and a substituent attached to the ring. The substituent is a chiral center due to the wedge and dash bonds indicating stereochemistry.

Step 2: Determine the stereochemical possibilities for the double bond. A double bond in an alkene can exhibit cis-trans (E/Z) isomerism depending on the relative positions of the substituents attached to the double-bonded carbons.

Step 3: Evaluate the chiral center. The substituent attached to the cyclohexene ring has a chiral center, which can exist in two configurations: R and S. This adds additional stereoisomeric possibilities.

Step 4: Combine the stereochemical possibilities. The total number of stereoisomers is determined by multiplying the possibilities from the double bond (E/Z) and the chiral center (R/S).

Step 5: Conclude the calculation. Since there are 2 possibilities for the double bond (E/Z) and 2 possibilities for the chiral center (R/S), the total number of stereoisomers is 2 × 2 = 4.

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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 their atoms. This can lead to different physical and chemical properties. In alkenes, stereoisomers arise due to the presence of a double bond, which restricts rotation and can create different configurations, such as cis and trans isomers.

Chirality and Enantiomers

Chirality is a property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of a chiral center, typically a carbon atom bonded to four different substituents. Enantiomers are a type of stereoisomer that are mirror images of each other and can exhibit different biological activities. Understanding chirality is crucial for determining the number of stereoisomers in a compound.

Counting Stereoisomers

The number of possible stereoisomers for a compound can be calculated using the formula 2^n, where n is the number of chiral centers in the molecule. For alkenes, the presence of double bonds and the possibility of cis/trans configurations must also be considered. This systematic approach helps in determining the total stereoisomer count for a given alkene structure.

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Related Practice

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical

(a)

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical

(e)

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical

(f)

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical

(h)

Textbook Question

How many stereoisomers are possible for each of the following molecules?

(e)

Textbook Question

Define the relationship between each set of two molecules as chain isomers, positional isomers, functional group isomers, enantiomers, diastereomers, conformational isomers, or identical.

(c)

Textbook Question

If the carbon atom in CH₂Cl₂ were flat, there would be two stereoisomers. The carbon atom in CH₂Cl₂is actually tetrahedral. Make a model of this compound, and determine whether there are any stereoisomers of CH₂Cl₂.