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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2:19 minutes

Problem 14b

Textbook Question

For each of the following chiral molecules, obtain the enantiomer (i) by drawing the nonsuperimposable mirror image and (ii) by switching the spatial orientation at each asymmetric center. Confirm (possibly using models) that the structures you drew for (i) and (ii) are the same.
(b)

Verified step by step guidance

Identify the chiral center(s) in the given molecule. A chiral center is typically a carbon atom bonded to four different groups. Ensure you clearly mark these centers for reference.

To obtain the enantiomer by drawing the nonsuperimposable mirror image (step i), imagine a mirror placed next to the molecule. Reflect each group attached to the chiral center(s) across the mirror. The positions of the groups should be reversed as if viewed in a mirror.

To obtain the enantiomer by switching the spatial orientation at each asymmetric center (step ii), invert the configuration of each chiral center. This means swapping the positions of any two groups attached to the chiral center. For example, if the groups are arranged in a clockwise (R) configuration, switch them to create a counterclockwise (S) configuration, or vice versa.

Compare the structures obtained in steps (i) and (ii). Use molecular models or visualization tools if necessary to confirm that the two structures are identical. This confirms that both methods yield the same enantiomer.

Verify that the enantiomer is nonsuperimposable on the original molecule. This ensures that the molecule and its enantiomer are true stereoisomers and not identical.

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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. Molecules that possess chirality typically have one or more asymmetric carbon atoms, leading to two distinct forms known as enantiomers. These enantiomers exhibit different optical activities and can have different biological activities, making chirality a crucial concept in organic chemistry.

Enantiomers

Enantiomers are a pair of chiral molecules that are mirror images of each other. They have identical physical properties, such as melting and boiling points, but differ in how they interact with polarized light and with other chiral substances. Understanding enantiomers is essential for predicting the behavior of chiral compounds in chemical reactions and biological systems.

Stereochemistry

Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this arrangement affects their chemical behavior. It encompasses concepts such as chirality, enantiomers, and diastereomers. In the context of the question, switching the spatial orientation at each asymmetric center is a stereochemical operation that helps in identifying the enantiomer of a given chiral molecule.

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Related Practice

Textbook Question

How many stereoisomers are possible for the following alkenes?

(b)

Textbook Question

For each of the compounds described by the following names,1. draw a three-dimensional representation.2. star (*) each chiral center.3. draw any planes of symmetry.4. draw any enantiomer.5. draw any diastereomers.6. label each structure you have drawn as chiral or achiral.c. (2R,3S)-2,3-dibromohexaned. (1R,2R)-1,2-dibromocyclohexane

Textbook Question

For each of the compounds described by the following names,

1. draw a three-dimensional representation.

2. star (*) each chiral center.

3. draw any planes of symmetry.

4. draw any enantiomer.

5. draw any diastereomers.

6. label each structure you have drawn as chiral or achiral.

c. (2R,3S)-2,3-dibromohexane

d. (1R,2R)-1,2-dibromocyclohexane

Textbook Question

Natural products are organic compounds produced by living organisms, including plants, fungi, and animals. Often referred to as secondary metabolites because they are not required for survival of the organism, natural products have found broad utility as drugs themselves or as lead compounds used in the development of medicines. One such example is paclitaxel, which has been used as a cancer drug. Paclitaxel is isolated from the yew tree, where it is produced as a single stereoisomer (shown). Based on its structure, how many stereoisomers are possible for paclitaxel?

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.

(c)

(d) 1-bromo-2-methylbutane

Textbook Question

3,4-Dimethylpent-1-ene has the formula CH₂=CH—CH(CH₃)—CH(CH₃)₂. When pure (R)-3,4-dimethylpent-1-ene is treated with hydrogen over a platinum catalyst, the product is (S)-2,3-dimethylpentane.

d. How useful is the (R) or (S) designation for predicting the sign of an optical rotation? Can you predict the sign of the rotation of the reactant? Of the product? (Hint from Juliet Capulet: “What’s in a name? That which we call a rose/By any other name would smell as sweet.”)

Textbook Question

To show that (R)-2-butyl (R,R)-tartrate and (S)-2-butyl (R,R)-tartrate are not enantiomers, draw and name the mirror images of these compounds.

Textbook Question

To show that (R)-2-butyl (R,R)-tartrate and (S)-2-butyl (R,R)-tartrate are not enantiomers, draw and name the mirror images of these compounds.

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