Draw curved arrows to show the movement of electrons in this step of the mechanism.

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ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
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Draw curved arrows to show the movement of electrons in this step of the mechanism. 

**Electrophilic Addition of Bromine to Alkenes**

The electrophilic addition of bromine (Br₂) to alkenes results in the formation of a 1,2-dibromoalkane. This reaction utilizes a cyclic intermediate known as a bromonium ion and typically occurs in an anhydrous solvent like CH₂Cl₂.

### Reaction Mechanism

1. **Formation of Bromonium Ion:**
   - The alkene reacts with Br₂, forming a bromonium ion intermediate.
   - This cyclic structure temporarily creates a positive charge on the bromonium ion.

2. **Nucleophilic Attack by Bromide:**
   - A bromide ion (now acting as a nucleophile) attacks one of the carbons in the bromonium ion.
   - This attack happens from the opposite side of the bromonium ion due to steric hindrance, resulting in anti stereochemistry.

### Diagram Explanation

- **Initial Reactants:**
  - An alkene molecule with a double bond between two carbon atoms, each bonded to methyl groups (CH₃).
  - Br₂ is added in the presence of CH₂Cl₂.

- **Intermediate Structure:**
  - The cyclic bromonium ion is shown with a positive charge.
  - A lone pair on the bromide ion is ready to make the nucleophilic attack.

- **Final Product:**
  - 1,2-dibromoalkane is formed with two bromine atoms attached to adjacent carbon atoms.

### Instruction on Electron Movement

- Curved arrows should be drawn to indicate the flow of electrons during these steps of the mechanism.

> **Note:** Use the blue "Arrow-pushing Instructions" button to practice drawing electron movement accurately.

### Additional Resources

- **Arrow-Pushing Guidance:**
  - Understanding the electron movement is crucial for mastering electrophilic addition reactions. Use available tools to simulate these interactions.
Transcribed Image Text:**Electrophilic Addition of Bromine to Alkenes** The electrophilic addition of bromine (Br₂) to alkenes results in the formation of a 1,2-dibromoalkane. This reaction utilizes a cyclic intermediate known as a bromonium ion and typically occurs in an anhydrous solvent like CH₂Cl₂. ### Reaction Mechanism 1. **Formation of Bromonium Ion:** - The alkene reacts with Br₂, forming a bromonium ion intermediate. - This cyclic structure temporarily creates a positive charge on the bromonium ion. 2. **Nucleophilic Attack by Bromide:** - A bromide ion (now acting as a nucleophile) attacks one of the carbons in the bromonium ion. - This attack happens from the opposite side of the bromonium ion due to steric hindrance, resulting in anti stereochemistry. ### Diagram Explanation - **Initial Reactants:** - An alkene molecule with a double bond between two carbon atoms, each bonded to methyl groups (CH₃). - Br₂ is added in the presence of CH₂Cl₂. - **Intermediate Structure:** - The cyclic bromonium ion is shown with a positive charge. - A lone pair on the bromide ion is ready to make the nucleophilic attack. - **Final Product:** - 1,2-dibromoalkane is formed with two bromine atoms attached to adjacent carbon atoms. ### Instruction on Electron Movement - Curved arrows should be drawn to indicate the flow of electrons during these steps of the mechanism. > **Note:** Use the blue "Arrow-pushing Instructions" button to practice drawing electron movement accurately. ### Additional Resources - **Arrow-Pushing Guidance:** - Understanding the electron movement is crucial for mastering electrophilic addition reactions. Use available tools to simulate these interactions.
**Electrophilic Addition of Bromine to Alkenes**

The electrophilic addition of bromine, Br₂, to alkenes yields a 1,2-dibromoalkane. This reaction proceeds through a cyclic intermediate known as a bromonium ion. The reaction occurs in an anhydrous solvent such as CH₂Cl₂.

In the second step of the reaction, bromide is the nucleophile and attacks one of the carbons of the bromonium ion to yield the product. Due to steric clashes, the bromide ion always attacks the carbon from the opposite face of the bromonium ion, resulting in a product with anti stereochemistry.

**Mechanism Details:**

- **Arrow-pushing Instructions:** The instruction section indicates how electrons move during the reaction process, represented by curved arrows.

**Diagram Explanation:**

The diagram shows the following process:

1. **Reactants:** On the left, there's a Br-Br molecule and an alkene with the structure H₃C-CH=CH₂.
   
2. **Intermediate Formation:** An arrow points from the reactants to the formation of a bromonium ion intermediate. This intermediate has a three-membered ring with a positively charged bromine atom (Br⁺) bonded to the carbons of the alkene. Another bromine ion (Br⁻) is shown as a separate entity.

3. **Outcome:** The nucleophilic Br⁻ will attack the bromonium ion from the opposite side, leading to the final dibromoalkane product (not shown in the image).

This step-by-step process illustrates the electrophilic addition mechanism with anti stereochemistry through the formation of a cyclic bromonium ion intermediate.
Transcribed Image Text:**Electrophilic Addition of Bromine to Alkenes** The electrophilic addition of bromine, Br₂, to alkenes yields a 1,2-dibromoalkane. This reaction proceeds through a cyclic intermediate known as a bromonium ion. The reaction occurs in an anhydrous solvent such as CH₂Cl₂. In the second step of the reaction, bromide is the nucleophile and attacks one of the carbons of the bromonium ion to yield the product. Due to steric clashes, the bromide ion always attacks the carbon from the opposite face of the bromonium ion, resulting in a product with anti stereochemistry. **Mechanism Details:** - **Arrow-pushing Instructions:** The instruction section indicates how electrons move during the reaction process, represented by curved arrows. **Diagram Explanation:** The diagram shows the following process: 1. **Reactants:** On the left, there's a Br-Br molecule and an alkene with the structure H₃C-CH=CH₂. 2. **Intermediate Formation:** An arrow points from the reactants to the formation of a bromonium ion intermediate. This intermediate has a three-membered ring with a positively charged bromine atom (Br⁺) bonded to the carbons of the alkene. Another bromine ion (Br⁻) is shown as a separate entity. 3. **Outcome:** The nucleophilic Br⁻ will attack the bromonium ion from the opposite side, leading to the final dibromoalkane product (not shown in the image). This step-by-step process illustrates the electrophilic addition mechanism with anti stereochemistry through the formation of a cyclic bromonium ion intermediate.
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