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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6:04 minutes

Problem 38a,b

Textbook Question

When pure (S)-lactic acid is esterified by racemic butan-2-ol, the product is 2-butyl lactate, with the following structure:

(a) Draw three-dimensional structures of the two stereoisomers formed, specifying the configuration at each asymmetric carbon atom. (Using your models may be helpful.)
(b) Determine the relationship between the two stereoisomers you have drawn

Verified step by step guidance

Step 1: Analyze the reaction. The esterification of (S)-lactic acid with racemic butan-2-ol produces 2-butyl lactate. The reaction involves the formation of an ester bond between the carboxylic acid group of lactic acid and the hydroxyl group of butan-2-ol.

Step 2: Identify the stereocenters. (S)-lactic acid has one stereocenter at the carbon bearing the hydroxyl group. Racemic butan-2-ol has one stereocenter at the carbon bearing the hydroxyl group. The product, 2-butyl lactate, will have two stereocenters: one from lactic acid and one from butan-2-ol.

Step 3: Draw the two stereoisomers of 2-butyl lactate. Since butan-2-ol is racemic, it contains both (R)- and (S)-enantiomers. When combined with (S)-lactic acid, the two possible products are (S,S)-2-butyl lactate and (S,R)-2-butyl lactate. Draw these structures in three dimensions, showing the configurations at each stereocenter.

Step 4: Determine the relationship between the two stereoisomers. The two stereoisomers, (S,S)-2-butyl lactate and (S,R)-2-butyl lactate, are diastereomers. Diastereomers are stereoisomers that are not mirror images of each other and have different physical and chemical properties.

Step 5: Verify the configurations. Use the Cahn-Ingold-Prelog priority rules to confirm the absolute configurations at each stereocenter in the two stereoisomers. This ensures that the structures are correctly assigned as (S,S) and (S,R).

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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 isomerism, particularly in compounds with chiral centers, where the arrangement of substituents around the asymmetric carbon can lead to different stereoisomers. In this context, recognizing the configurations (R or S) of the chiral centers in lactic acid and butan-2-ol is essential for drawing the correct three-dimensional structures.

Esterification Reaction

Esterification is a chemical reaction between an alcohol and a carboxylic acid, resulting in the formation of an ester and water. In this case, the reaction between (S)-lactic acid and racemic butan-2-ol produces 2-butyl lactate. Understanding the mechanism of esterification, including the role of the hydroxyl group and the carboxyl group, is important for predicting the products and their stereochemical outcomes.

Stereoisomer Relationship

The relationship between stereoisomers can be classified as enantiomers or diastereomers, depending on their configurations. Enantiomers are non-superimposable mirror images, while diastereomers are not mirror images and differ at one or more chiral centers. In this question, determining whether the two stereoisomers of 2-butyl lactate are enantiomers or diastereomers is key to understanding their chemical properties and reactivity.

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Related Practice

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.

(b)

Textbook Question

Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?

Textbook Question

Do the following structures represent identical compounds or a pair of enantiomers?

Textbook Question

For each of the stereocenters (circled) in Figure 5-5,

a. draw the compound with two of the groups on the stereocenter interchanged.

b. give the relationship of the new compound to the original compound.

Textbook Question

What type of isomerism is indicated by each of the following pairs of molecules? Be as specific as possible.

(a)

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)

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