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

10. Addition Reactions

Alkyne Hydrohalogenation

Organic Chemistry

10. Addition Reactions

Alkyne Hydrohalogenation

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Problem 34b

Textbook Question

Predict the alkyne and reactants you might use to make the following haloalkenes. [Providing the reactant and the reagent is how we start thinking about synthesis.]
(b)

Verified step by step guidance

Analyze the target molecule: The product is a haloalkene with a bromine atom attached to a double bond. The structure suggests that the alkyne precursor underwent a selective addition reaction.

Identify the reaction type: To synthesize a haloalkene from an alkyne, a hydrohalogenation reaction is typically used. This involves adding HX (where X is a halogen, such as Br) to the alkyne under controlled conditions to stop at the alkene stage.

Determine the alkyne precursor: The alkyne precursor should have the same carbon skeleton as the product but with a triple bond in place of the double bond. In this case, the alkyne would be 1-cyclohexyl-2-cyclohexylacetylene.

Select the reagent: Use HBr as the reagent for hydrohalogenation. The reaction conditions should be controlled to ensure the addition stops at the alkene stage rather than proceeding to the alkane.

Consider regioselectivity: The Markovnikov rule applies here, meaning the bromine atom will add to the more substituted carbon of the double bond, resulting in the observed product.

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Key Concepts

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

Alkynes

Alkynes are hydrocarbons that contain at least one carbon-carbon triple bond. They are unsaturated compounds and can undergo various reactions, including addition reactions. Understanding the structure and reactivity of alkynes is crucial for predicting the products of synthetic pathways, such as the formation of haloalkenes.

Haloalkenes

Haloalkenes, or alkyl halides, are alkenes that contain a halogen atom (like bromine) attached to one of the carbon atoms in the double bond. The presence of the halogen influences the reactivity and properties of the compound, making it important to consider when predicting synthesis routes and selecting appropriate reactants.

Synthesis Strategies

Synthesis strategies in organic chemistry involve planning a series of chemical reactions to construct a desired compound from simpler starting materials. This includes identifying the necessary reactants and reagents, as well as understanding the mechanisms of the reactions involved. Effective synthesis requires knowledge of functional group transformations and reaction conditions.

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Related Practice

Textbook Question

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (v) HCl (2 equiv.). If you expect two products, show both.

(c)

Textbook Question

Predict the alkyne and reactants you might use to make the following haloalkenes. [Providing the reactant and the reagent is how we start thinking about synthesis.]

(a)

Textbook Question

HBr and peroxides are also used to generate 1-bromo-1-alkenes. Suggest a starting reactant that would successfully undergo this reaction.

Textbook Question

Predict the major products resulting from the addition of one equivalent of HX to the following alkynes.

(b)

Textbook Question

The addition of H―X to alkynes has been shown to occur predominately via anti addition:

Two chemists disagreed on whether or not anti addition would happen on terminal alkynes as well. Suggest an experiment through which you could resolve this dispute.

Textbook Question

What is the major product obtained from the reaction of each of the following compounds with excess HCl?

c. CH₃CH₂C☰CCH₂CH₂CH₃

Textbook Question

Answer Problem 39, parts a–h, using 2-butyne as the starting material instead of propyne.

a. HBr (1 mol)

b. HBr (2 mol)

Textbook Question

Predict the major product(s) of the following reactions:

c. cyclooctyne + 2 HBr

d. *hex-2-yne + 2 HCl

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