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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2:23 minutes

Problem 64a

Textbook Question

Thiols can be prepared from the reaction of thiourea with an alkyl halide, followed by hydroxide-ion-promoted hydrolysis.
a. Propose a mechanism for the reaction.

Verified step by step guidance

Step 1: Recognize the reaction components. Thiourea (NH2-CS-NH2) reacts with an alkyl halide (R-X) in the first step. The alkyl halide is an electrophile, and thiourea acts as a nucleophile due to the lone pair on the sulfur atom.

Step 2: Describe the nucleophilic substitution reaction. The sulfur atom in thiourea attacks the carbon atom of the alkyl halide (R-X), displacing the halide ion (X⁻) and forming an intermediate called an alkylisothiouronium salt (R-NH-CS-NH2). This is an SN2 reaction mechanism.

Step 3: Introduce the hydrolysis step. The alkylisothiouronium salt undergoes hydroxide-ion-promoted hydrolysis. The hydroxide ion (OH⁻) attacks the carbon atom of the C=S bond in the intermediate, leading to the cleavage of the C=S bond.

Step 4: Explain the formation of the thiol. The hydrolysis results in the release of the thiol (R-SH) and urea (NH2-CO-NH2) as byproducts. This step involves breaking the C=S bond and replacing it with a C-SH bond.

Step 5: Summarize the overall mechanism. The reaction proceeds via two main steps: (1) nucleophilic substitution of the alkyl halide by thiourea to form the alkylisothiouronium salt, and (2) hydroxide-ion-promoted hydrolysis of the intermediate to yield the thiol and urea.

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Key Concepts

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

Thiourea Structure and Reactivity

Thiourea is a compound containing a sulfur atom bonded to a carbon atom and two amine groups. Its structure allows it to act as a nucleophile in reactions with alkyl halides, where the sulfur atom can attack the electrophilic carbon of the halide, leading to the formation of a thiol. Understanding the reactivity of thiourea is crucial for proposing the mechanism of thiol synthesis.

Nucleophilic Substitution Mechanism

Nucleophilic substitution is a fundamental reaction mechanism in organic chemistry where a nucleophile replaces a leaving group in a substrate. In the case of thiourea reacting with an alkyl halide, the sulfur atom acts as the nucleophile, attacking the carbon atom bonded to the halide. This process can follow either an SN1 or SN2 pathway, depending on the structure of the alkyl halide and reaction conditions.

Hydroxide-Ion-Promoted Hydrolysis

Hydroxide-ion-promoted hydrolysis involves the reaction of a compound with water in the presence of hydroxide ions, which can facilitate the breaking of bonds and the formation of new ones. In the context of thiol synthesis, after the nucleophilic substitution, hydroxide ions can help hydrolyze any intermediates formed, ultimately leading to the production of the desired thiol. This step is essential for completing the reaction mechanism.

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Thiols can be prepared from the reaction of thiourea with an alkyl halide, followed by hydroxide-ion-promoted hydrolysis. a. Propose a mechanism for the reaction.

Key Concepts

Thiourea Structure and Reactivity

Nucleophilic Substitution Mechanism

Hydroxide-Ion-Promoted Hydrolysis

Watch next

Thiols can be prepared from the reaction of thiourea with an alkyl halide, followed by hydroxide-ion-promoted hydrolysis.
a. Propose a mechanism for the reaction.