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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6:23 minutes

Problem 20a,b

Textbook Question

For each pair, give the relationship between the two compounds. Making models will be helpful.
(a) (2R,3S)-2,3-dibromohexane and (2S,3R)-2,3-dibromohexane
(b) (2R,3S)-2,3-dibromohexane and (2R,3R)-2,3-dibromohexane

Verified step by step guidance

Step 1: Understand the problem. The question asks for the relationship between two pairs of compounds. To determine the relationship, we need to analyze the stereochemistry of the given compounds. Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their properties.

Step 2: Analyze part (a). Compare (2R,3S)-2,3-dibromohexane and (2S,3R)-2,3-dibromohexane. Note that the stereochemistry at both chiral centers is inverted between the two compounds. This means the configuration at carbon 2 changes from R to S, and at carbon 3 changes from S to R. When all chiral centers are inverted, the compounds are enantiomers (non-superimposable mirror images).

Step 3: Analyze part (b). Compare (2R,3S)-2,3-dibromohexane and (2R,3R)-2,3-dibromohexane. Here, the configuration at carbon 2 remains the same (R), but the configuration at carbon 3 changes from S to R. When only one chiral center is inverted, the compounds are diastereomers (stereoisomers that are not mirror images).

Step 4: Summarize the relationships. For part (a), the compounds are enantiomers because all chiral centers are inverted. For part (b), the compounds are diastereomers because only one chiral center is inverted.

Step 5: Optional verification. If you have access to molecular models, build models of the compounds to visualize their spatial arrangements. This can help confirm the relationships determined in the previous steps.

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Key Concepts

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

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. It is crucial for understanding isomers, particularly enantiomers and diastereomers, which differ in the orientation of their substituents around chiral centers. In the given question, the stereochemical configurations of the compounds are essential for determining their relationships.

Chirality

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, much like left and right hands. Chiral molecules typically have one or more chiral centers, which are carbon atoms bonded to four different substituents. The (2R,3S) and (2S,3R) configurations in the question indicate different chiral arrangements, leading to the formation of enantiomers.

Enantiomers and Diastereomers

Enantiomers are pairs of chiral molecules that are mirror images of each other, while diastereomers are stereoisomers that are not mirror images. The relationship between (2R,3S)-2,3-dibromohexane and (2S,3R)-2,3-dibromohexane is that they are enantiomers, whereas the relationship between (2R,3S)-2,3-dibromohexane and (2R,3R)-2,3-dibromohexane is that they are diastereomers, as they differ in configuration at one chiral center but not the other.

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Related Practice

Textbook Question

For each of the following molecules, identify all stereocenters and draw all possible stereoisomers.

(f)

Textbook Question

For each of the following molecules, identify all stereocenters and draw all possible stereoisomers.

(b)

Textbook Question

Draw a three-dimensional structure for each compound, and star all asymmetric carbon atoms. Draw the mirror image for each structure, and state whether you have drawn a pair of enantiomers or just the same molecule twice.Build molecular models of any of these examples that seem difficult to youe. Chlorocyclohexanef. Cis-1,2-dichlorocyclobutane

Textbook Question

Draw a three-dimensional structure for each compound, and star all asymmetric carbon atoms. Draw the mirror for each structure, and state whether you have drawn a pair of enantiomers or just the same molecule twice. Build molecular models of any of these examples that seem difficult to you.

(e) chlorocyclohexane

(f) cis-1,2-dichlorocyclobutane

Textbook Question

For the compound 1-ethyl-3-isopropylcyclopentane,

(b) What is the stereochemical relationship between the cis isomers?

Textbook Question

(a) Give the products expected when (+)@glyceraldehyde reacts with HCN.(b) What is the relationship between the products? How might they be separated?(c) Are the products optically active? Explain.

Textbook Question

(a) Give the products expected when (+)-glyceraldehyde reacts with HCN.

(b) What is the relationship between the products? How might they be separated?

Textbook Question

For the compound 1-ethyl-3-isopropylcyclopentane,