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

12. Alcohols, Ethers, Epoxides and Thiols

Thiol Reactions

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Thiol Reactions

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6:42 minutes

Problem 37

Textbook Question

(a) Show how you would synthesize the pure (R) enantiomer of 2-butyl methyl sulfide, starting with pure (R)-butan-2-ol and any reagents you need
(b) Show how you would synthesize the pure (S) enantiomer of the product, still starting with (R)-butan-2-ol and any reagents you need.

Verified step by step guidance

Step 1: Begin with the pure (R)-butan-2-ol as the starting material. The hydroxyl group (-OH) needs to be converted into a good leaving group to facilitate substitution. React (R)-butan-2-ol with a reagent like p-toluenesulfonyl chloride (TsCl) in the presence of a base such as pyridine to form the (R)-butan-2-yl tosylate. This step retains the stereochemistry of the starting material.

Step 2: To synthesize the (R)-enantiomer of 2-butyl methyl sulfide, perform a nucleophilic substitution reaction. React the (R)-butan-2-yl tosylate with sodium methyl sulfide (CH₃S⁻Na⁺). The methyl sulfide anion will attack the carbon attached to the tosylate group, displacing the tosylate and forming (R)-2-butyl methyl sulfide. This reaction proceeds via an SN2 mechanism, which inverts the stereochemistry. Since the starting material is (R)-butan-2-yl tosylate, the inversion results in the (R)-enantiomer of the product.

Step 3: To synthesize the (S)-enantiomer of 2-butyl methyl sulfide, you need to invert the stereochemistry of the starting material before proceeding with the substitution reaction. React (R)-butan-2-ol with a reagent like thionyl chloride (SOCl₂) in the presence of pyridine to form (S)-butan-2-yl chloride. This reaction proceeds via an SN2 mechanism, which inverts the stereochemistry of the alcohol to form the (S)-enantiomer of the alkyl chloride.

Step 4: Perform a nucleophilic substitution reaction to convert (S)-butan-2-yl chloride into (S)-2-butyl methyl sulfide. React (S)-butan-2-yl chloride with sodium methyl sulfide (CH₃S⁻Na⁺). The methyl sulfide anion will attack the carbon attached to the chloride group, displacing the chloride and forming (S)-2-butyl methyl sulfide. This reaction proceeds via an SN2 mechanism, which retains the stereochemistry of the starting material.

Step 5: Verify the stereochemistry of the products using techniques such as polarimetry or chiral chromatography to ensure that the desired (R)- and (S)-enantiomers of 2-butyl methyl sulfide have been synthesized.

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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. In organic chemistry, understanding stereochemistry is crucial for distinguishing between enantiomers, which are molecules that are mirror images of each other. The (R) and (S) designations refer to the specific three-dimensional configurations of chiral centers in a molecule, which directly influence the properties and reactivity of the compounds.

Chiral Centers

A chiral center, often a carbon atom, is bonded to four different substituents, leading to non-superimposable mirror images. The presence of chiral centers in a molecule is what gives rise to enantiomers. In the synthesis of 2-butyl methyl sulfide, recognizing and manipulating these chiral centers is essential for producing the desired (R) or (S) enantiomer, as the configuration must be preserved or inverted appropriately during the synthesis process.

Reagents and Reaction Mechanisms

The choice of reagents and understanding the reaction mechanisms are vital for synthesizing specific organic compounds. Different reagents can facilitate various types of reactions, such as nucleophilic substitutions or eliminations, which are crucial for forming or modifying chiral centers. In this synthesis, selecting the right reagents will determine whether the (R) or (S) enantiomer is produced, as well as the efficiency and yield of the overall reaction.

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Show how you would synthesize the following:

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Authentic skunk spray has become valuable for use in scent-masking products. Show how you would synthesize the major component of skunk spray (3-methylbutane-1-thiol and but-2-ene-1-thiol) from any of the readily available butene or from buta-1,3-diene.

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(a) Show how you would synthesize the pure (R) enantiomer of 2-butyl methyl sulfide, starting with pure (R)-butan-2-ol and any reagents you need(b) Show how you would synthesize the pure (S) enantiomer of the product, still starting with (R)-butan-2-ol and any reagents you need.

Key Concepts

Stereochemistry

Chiral Centers

Reagents and Reaction Mechanisms

Watch next

(a) Show how you would synthesize the pure (R) enantiomer of 2-butyl methyl sulfide, starting with pure (R)-butan-2-ol and any reagents you need
(b) Show how you would synthesize the pure (S) enantiomer of the product, still starting with (R)-butan-2-ol and any reagents you need.