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

Leaving Group Conversions Summary

Organic Chemistry

12. Alcohols, Ethers, Epoxides and Thiols

Leaving Group Conversions Summary

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5:50 minutes

Problem 41a,b

Textbook Question

In each case, show how you would synthesize the chloride, bromide, and iodide from the corresponding alcohol.
(a) 1-halobutane (halo = chloro, bromo, iodo)
(b) halocyclopentane

Verified step by step guidance

Step 1: Recognize that the synthesis of alkyl halides (chlorides, bromides, and iodides) from alcohols typically involves substitution reactions where the hydroxyl group (-OH) is replaced by a halogen atom. Common reagents for this transformation include thionyl chloride (SOCl₂), phosphorus tribromide (PBr₃), and iodine with phosphorus (I₂/P).

Step 2: For part (a), 1-halobutane: Start with 1-butanol (CH₃CH₂CH₂CH₂OH). To synthesize 1-chlorobutane, react 1-butanol with thionyl chloride (SOCl₂) in the presence of pyridine. The reaction proceeds via an SN2 mechanism, replacing the -OH group with a chlorine atom.

Step 3: For 1-bromobutane, react 1-butanol with phosphorus tribromide (PBr₃). This reaction also proceeds via an SN2 mechanism, where the hydroxyl group is replaced by a bromine atom.

Step 4: To synthesize 1-iodobutane, react 1-butanol with iodine (I₂) and red phosphorus (P). The phosphorus reacts with iodine to form PI₃ in situ, which then substitutes the hydroxyl group with an iodine atom.

Step 5: For part (b), halocyclopentane: Start with cyclopentanol (C₅H₁₀OH). Follow the same procedures as above for each halogen: (i) React cyclopentanol with SOCl₂ for chlorocyclopentane, (ii) React cyclopentanol with PBr₃ for bromocyclopentane, and (iii) React cyclopentanol with I₂/P for iodocyclopentane.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule with a nucleophile. In the context of synthesizing halides from alcohols, the hydroxyl group (-OH) of the alcohol acts as the leaving group, while halide ions (Cl-, Br-, I-) serve as nucleophiles. Understanding the mechanism (SN1 or SN2) is crucial, as it influences the reaction conditions and the structure of the starting alcohol.

Conversion of Alcohols to Halides

Alcohols can be converted to alkyl halides through various methods, including the use of reagents like thionyl chloride (SOCl2), phosphorus tribromide (PBr3), or hydrohalic acids (HCl, HBr, HI). These reagents facilitate the substitution of the hydroxyl group with a halogen, effectively transforming the alcohol into the desired halide. The choice of reagent often depends on the type of halide being synthesized and the structure of the alcohol.

Stereochemistry and Reactivity

The stereochemistry of the starting alcohol can significantly affect the outcome of the halide synthesis. For example, primary alcohols typically undergo SN2 reactions, leading to inversion of configuration, while tertiary alcohols often proceed via SN1 mechanisms, resulting in racemization. Understanding the reactivity patterns and stereochemical implications is essential for predicting the products of the halide synthesis from alcohols.