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

What is the Relationship Between Isomers?

Organic Chemistry

5. Chirality

What is the Relationship Between Isomers?

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1:35 minutes

Problem 35a

Textbook Question

For the molecules shown,
(i) count the number of stereocenters present and
(ii) draw all possible stereoisomers.
(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.
(a)

Verified step by step guidance

Step 1: Identify stereocenters in the molecule. A stereocenter is typically a carbon atom bonded to four different groups. Examine each carbon atom in the molecule and determine if it meets this criterion.

Step 2: Count the total number of stereocenters. Once all stereocenters are identified, count them to determine the total number present in the molecule.

Step 3: Calculate the maximum number of stereoisomers. Use the formula 2^n, where 'n' is the number of stereocenters, to determine the maximum number of possible stereoisomers for the molecule.

Step 4: Draw all possible stereoisomers. For each stereocenter, assign configurations (R or S) systematically to generate all combinations of stereoisomers. Ensure that you represent each stereoisomer with its correct 3D structure (e.g., using wedge and dash bonds).

Step 5: Identify relationships between stereoisomers. Compare the stereoisomers to determine if they are enantiomers (non-superimposable mirror images) or diastereomers (stereoisomers that are not mirror images). Use the configurations (R/S) to help classify these relationships.

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Key Concepts

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

Stereocenters

A stereocenter, or chiral center, is a carbon atom that is bonded to four different substituents, leading to non-superimposable mirror images known as enantiomers. The presence of stereocenters in a molecule is crucial for determining its stereochemistry and the number of possible stereoisomers. Each stereocenter can exist in two configurations, contributing to the overall stereoisomer count.

Stereoisomers

Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. They can be classified into two main types: enantiomers, which are non-superimposable mirror images, and diastereomers, which are not mirror images of each other. The number of stereoisomers for a molecule can be calculated using the formula 2^n, where n is the number of stereocenters.

Enantiomers and Diastereomers

Enantiomers are pairs of stereoisomers that are mirror images of each other, possessing opposite configurations at all stereocenters. In contrast, diastereomers differ in configuration at one or more stereocenters but not all, making them non-mirror images. Understanding these relationships is essential for predicting the behavior of molecules in chemical reactions and their interactions in biological systems.

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Related Practice

Textbook Question

Identify

1. constitutional isomers

2. stereoisomers

3. cis–trans isomers

4. chiral compounds

Textbook Question

Draw the mirror image of the following molecule. Then, using the mirror image generated, switch the spatial orientation at the asymmetric center. Is the final structure the enantiomer of the original? If not, what is it?

Textbook Question

For each pair, give the relationship between the two compounds. Making models will be helpful.

(h)

Textbook Question

Make a model and draw a three-dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each structure as being chiral or achiral, and label pairs of enantiomers.

(e)

(f)

Textbook Question

(i) Which of the following pairs of compounds would you expect to have different physical properties?

(ii) What is the relationship between each of the pairs?

(iii) Assign the absolute configuration of each stereocenter to confirm your answer.

(a)

Textbook Question

Draw the structure for a compound with molecular formula C₂H₂I₂F₂

a. that is optically inactive because it does not have an asymmetric center.

b. that is optically inactive because it is a meso compound.

Multiple Choice