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 Halogenation

Organic Chemistry

10. Addition Reactions

Alkyne Halogenation

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4:17 minutes

Problem 40d

Textbook Question

Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
d. Br₂ (2 mol)/CH₂Cl₂

Verified step by step guidance

Identify the starting material: The starting material is 2-butyne, which is a terminal alkyne with the structure CH3-C≡C-CH3.

Understand the reagent: The reagent is Br2 (2 mol) in CH2Cl2. Bromine (Br2) in an inert solvent like dichloromethane (CH2Cl2) is used to add bromine atoms across the triple bond of the alkyne.

Determine the reaction type: This is a halogenation reaction. When an alkyne reacts with 2 equivalents of Br2, the triple bond is fully saturated, resulting in a tetrahalide product.

Write the reaction mechanism: In the first step, one equivalent of Br2 adds across the triple bond, converting it into a dibromoalkene (CH3-CBr=CHBr-CH3). In the second step, the remaining equivalent of Br2 adds across the double bond, resulting in a tetrahalide (CH3-CBr2-CBr2-CH3).

Verify the product: The final product is 2,2,3,3-tetrabromobutane, where all four bromine atoms are added to the original carbon atoms of the triple bond.

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Key Concepts

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

Alkyne Reactivity

Alkynes, such as 2-butyne, are hydrocarbons with a carbon-carbon triple bond. This triple bond makes them more reactive than alkenes and alkanes, allowing them to undergo various addition reactions. Understanding the reactivity of alkynes is crucial for predicting the products formed when they react with halogens like Br2.

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, resulting in the formation of a more saturated compound. In the case of 2-butyne reacting with Br2, the triple bond acts as a nucleophile, attacking the electrophilic bromine, leading to the formation of a dibrominated product.

Stereochemistry of Addition Reactions

Stereochemistry refers to the spatial arrangement of atoms in molecules and how this affects their chemical behavior. When Br2 adds to 2-butyne, the stereochemical outcome can lead to different isomers, such as cis and trans forms, depending on the reaction conditions. Understanding stereochemistry is essential for predicting the specific products and their configurations in addition reactions.

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Related Practice

Textbook Question

What stereoisomers are obtained when 2-butyne undergoes each of the following reaction sequences?

c. 1. Cl₂/CH₂Cl₂ 2. Br₂/CH₂Cl₂

Textbook Question

What reagents should be used to carry out the following syntheses?

Multiple Choice

Predict the major, organic product of the following reaction.

Textbook Question

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?

d. Br₂ (2 mol)/CH₂Cl₂

Textbook Question

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

c. Br₂ (1 mol)/CH₂Cl₂

Textbook Question

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?

c. Br₂ (1 mol)/CH₂Cl₂

Textbook Question

In the addition of just 1 mole of bromine to 1 mole of hex-1-yne, should the hex-1-yne be added to a bromine solution or should the bromine be added to the hex-1-yne? Explain your answer.

Textbook Question

For the alkynes shows here, show the product(s) expected to form when treated under the following conditions: (viii) Cl₂ (1 equiv.). If you expect two products, show both.

(c)

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Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne. d. Br2 (2 mol)/CH2Cl2

Key Concepts

Alkyne Reactivity

Electrophilic Addition

Stereochemistry of Addition Reactions

Watch next

Answer Problem 39 , parts a–h, using 2-butyne as the starting material instead of propyne.
d. Br₂ (2 mol)/CH₂Cl₂