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

Atropisomers

Organic Chemistry

5. Chirality

Atropisomers

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4:44 minutes

Problem 77a,b

Textbook Question

Which of the following has an achiral stereoisomer?
a. 2,3-dichlorobutane
b. 2,3-dichloropentane

Verified step by step guidance

Step 1: Understand the concept of chirality. A molecule is chiral if it has a non-superimposable mirror image, typically due to the presence of a carbon atom bonded to four different groups. An achiral molecule, on the other hand, has a plane of symmetry or a center of symmetry, making it superimposable on its mirror image.

Step 2: Analyze the structure of 2,3-dichlorobutane. Draw the molecule and identify the stereocenters (chiral carbons). In this case, carbons 2 and 3 are stereocenters because they are bonded to four different groups.

Step 3: Determine if 2,3-dichlorobutane can have an achiral stereoisomer. Check for the possibility of a meso compound, which is an achiral molecule despite having stereocenters. A meso compound occurs when the molecule has an internal plane of symmetry that makes it superimposable on its mirror image.

Step 4: Repeat the analysis for 2,3-dichloropentane. Draw the molecule, identify the stereocenters (carbons 2 and 3), and check for the presence of an internal plane of symmetry that could result in a meso compound.

Step 5: Compare the findings for both molecules. Determine which molecule has an achiral stereoisomer (a meso form) based on the presence of an internal plane of symmetry. This will help you identify the correct answer.

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Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has at least one carbon atom bonded to four different substituents, resulting in two distinct enantiomers. Understanding chirality is crucial for identifying stereoisomers and their properties.

Stereoisomers

Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This category includes enantiomers, which are non-superimposable mirror images, and diastereomers, which are not mirror images. Recognizing the types of stereoisomers is essential for determining the presence of achiral forms.

Achirality

Achirality describes molecules that are superimposable on their mirror images, meaning they do not exhibit chirality. A molecule can be achiral if it has a plane of symmetry or if it lacks chiral centers. Identifying achiral stereoisomers is important in organic chemistry, as it influences the reactivity and properties of the compounds.

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Related Practice

Textbook Question

Draw three-dimensional representations of the following compounds. Which have asymmetric carbon atoms? Which have no asymmetric carbons but are chiral anyway? Use your models for parts (a) through (d) and any others that seem unclear.

(g)

Textbook Question

A compound with two chiral centers that is meso will always have opposite absolute configurations at the two chiral centers. That is, a meso compound will never be (R,R) or (S,S); instead, it will be (R,S). Explain why this must be true.

Textbook Question

Which of the following compounds has a stereoisomer that is a meso compound?

c. 2,4-dimethylpentane

d. 1,3-dichlorocyclohexane

Textbook Question

Which of the following compounds has a stereoisomer that is a meso compound?

a. 2,4-dibromohexane

b. 2,4-dibromopentane

Textbook Question

Which of the following compounds are chiral? Draw each compound in its most symmetric conformation, star (*) any asymmetric carbon atoms, and draw any mirror planes. Label any meso compounds. You may use Fischer projections if you prefer.

(d) (2R,3S)-2,3-dibromobutane

Textbook Question

Which of the following compounds are meso?

(e)

Textbook Question

Which of the following compounds are meso?

(g)

Textbook Question

For each structure,

1. star (*) any asymmetric carbon atoms.

2. label each asymmetric carbon as (R) or (S).

3. draw any internal mirror planes of symmetry.