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1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

13. Alkenes, Alkynes, and Aromatic Compounds

Halogenation Reaction

13. Alkenes, Alkynes, and Aromatic Compounds

Halogenation Reaction: Videos & Practice Problems

Video Lessons Practice Worksheet

Topic summary

Halogenation reactions involve the addition of halogens (X₂, such as Br₂ or Cl₂) to alkenes and alkynes. In alkenes, each double-bonded carbon gains one halogen, resulting in a dihalide. For alkynes, which contain two pi bonds, two moles of halogen are required, yielding a tetrahalide with four halogens. This process exemplifies an addition reaction, where the structure of the original hydrocarbon is modified by the introduction of functional groups, enhancing its chemical properties.

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Halogenation Reactions Concept 1

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Halogenation Reactions Concept 1 Video Summary

Halogenation reactions involve the addition of halogens, such as bromine (Br₂) or chlorine (Cl₂), to alkenes and alkynes. In these reactions, each double bond (π bond) in the starting alkene reacts with one mole of halogen, resulting in the formation of a dihalide. This means that for every π bond present, one mole of halogen is required, leading to the addition of two halogen atoms to the molecule.

For example, when an alkene undergoes halogenation, the two carbon atoms involved in the double bond each gain one halogen atom, resulting in a compound with two halogens, known as a dihalide. Conversely, in the case of an alkyne, which contains two π bonds, two moles of halogen are necessary. The first mole adds two halogens, and the second mole adds another two, yielding a compound with four halogen atoms, referred to as a tetrahalide.

In summary, halogenation is characterized by the addition of two halogens per π bond in the structure, producing either a dihalide from alkenes or a tetrahalide from alkynes.

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Halogenation Reactions Example 1

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Halogenation Reactions Example 1 Video Summary

In the halogenation reaction of an alkene with chlorine, the process involves the addition of two chlorine atoms across the double bond of the alkene. This reaction results in the formation of a dihalide. The key concept here is that the pi bond of the alkene is broken, allowing each carbon atom that was part of the double bond to bond with a chlorine atom.

When reacting with one mole of chlorine (Cl₂), the alkene undergoes a transformation where each of the double-bonded carbons becomes bonded to a chlorine atom. The orientation of the chlorines—whether they are positioned on the same side (cis) or opposite sides (trans)—is not critical for the basic understanding of the reaction at this stage. The primary focus is on ensuring that each carbon from the original double bond is now connected to a chlorine atom, resulting in a dihalide structure.

The general reaction can be represented as follows:

\[\text{Alkene} + \text{Cl}_2 \rightarrow \text{Dihalide}\]

In summary, the halogenation of an alkene with chlorine leads to the formation of a dihalide, where each carbon from the original double bond is now bonded to a chlorine atom, effectively sacrificing the pi bond in the process.

Problem

Write a halogenation reaction of the following alkyne with Br2 and name the product formed.

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Here’s what students ask on this topic:

What is a halogenation reaction in organic chemistry?

A halogenation reaction in organic chemistry involves the addition of halogen atoms (such as Br₂ or Cl₂) to a hydrocarbon. This reaction typically occurs with alkenes and alkynes. For alkenes, each carbon in the double bond gains one halogen, resulting in a dihalide. For alkynes, which have two pi bonds, two moles of halogen are required, leading to a tetrahalide with four halogens. This process is an example of an addition reaction, where the original hydrocarbon structure is modified by the introduction of halogen atoms, enhancing its chemical properties.

How does halogenation of alkenes differ from halogenation of alkynes?

Halogenation of alkenes and alkynes differs primarily in the number of halogen atoms added. In alkenes, each double-bonded carbon gains one halogen atom, resulting in a dihalide. The general reaction can be represented as:

$R CH = CH R + X_{2} \to R CH X_{2} CH R$

For alkynes, which contain two pi bonds, two moles of halogen are required. The first mole adds two halogens, and the second mole adds another two, resulting in a tetrahalide:

$R C \equiv C R + 2 X_{2} \to R C X_{2} C X_{2} R$

What are the products of halogenation of an alkene?

The products of halogenation of an alkene are dihalides. In this reaction, each carbon atom in the double bond of the alkene gains one halogen atom. For example, if we start with ethene (C₂H₄) and react it with bromine (Br₂), the product will be 1,2-dibromoethane (C₂H₄Br₂):

$CH 2 = CH 2 + {Br}_{2} \to CH 2 Br CH 2 Br$

This reaction is an example of an addition reaction, where the double bond is broken, and two new single bonds are formed with the halogen atoms.

Why are halogenation reactions important in organic chemistry?

Halogenation reactions are important in organic chemistry because they allow for the functionalization of hydrocarbons, making them more reactive and versatile for further chemical transformations. By adding halogens to alkenes and alkynes, chemists can create dihalides and tetrahalides, which serve as key intermediates in the synthesis of various organic compounds. These reactions are also used in the production of pharmaceuticals, agrochemicals, and polymers. Additionally, halogenation can help in the study of reaction mechanisms and the development of new synthetic methodologies.

What is the mechanism of halogenation of alkenes?

The mechanism of halogenation of alkenes involves a three-step process:

1. **Formation of the Halonium Ion:** The alkene reacts with a halogen molecule (X₂), forming a cyclic halonium ion intermediate. This occurs when the pi electrons of the alkene attack the halogen molecule, leading to the formation of a three-membered ring with a positive charge on the halogen.

2. **Nucleophilic Attack:** The halonium ion is then attacked by a halide ion (X^-), which opens the three-membered ring and forms a vicinal dihalide.

3. **Formation of the Dihalide:** The final product is a dihalide, where each carbon of the original double bond is bonded to a halogen atom.

This mechanism ensures the anti-addition of halogens, meaning the halogens add to opposite sides of the former double bond.

Previous Topic: Intro to Addition Reactions Next Topic: Hydrogenation Reaction

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