Which arrow-pushing mechanism best explains the bromination of the following alkene shown below?©GMU 2020 Br2 Me OMe C5HgO2Br2 CCI4 O The following mechanism: H (Br Me OMe Br O The following mechanism: Br-Br OMe Me H. O The following mechanism: COME H. Me., Br OMe Br O The following mechanism: H. (Br OMe H. Me Br

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### Exploring Bromination Mechanisms of Alkenes

**Question:**
Which arrow-pushing mechanism best explains the bromination of the following alkene shown below?

- **Reaction:**  
  \[ \text{MeO}C=C(\text{Me})C=O\] 
  - Reagent: \( \text{Br}_2 \)
  - Solvent: \( \text{CCl}_4 \)
  - Product: \( \text{C}_5\text{H}_8\text{O}_2\text{Br}_2 \)

**Options:**

1. **Mechanism 1:**
   - The double bond attacks a bromine (Br) in \( \text{Br}_2 \), forming a bromonium ion. The bromide ion then attacks a carbon, opening the bromonium ion.
  
2. **Mechanism 2:**
   - The bromine molecule adds across the double bond without forming a bromonium ion, showing a concerted mechanism.

3. **Mechanism 3:**
   - An initial lone pair on an oxygen atom forms a double bond, pushing electrons through the molecule and attacking \( \text{Br}_2 \), forming a cyclic structure involving bromine.

4. **Mechanism 4:**
   - The double bond forms a bromonium ion with one bromine, followed by the attack of the bromide ion on one of the carbons of the ion, opening the bromonium.

Each mechanism involves intricate electron movements where bromine interacts with the double bond in the alkene, highlighting the importance of understanding arrow-pushing in chemical reactions.

The correct answer will demonstrate the typical mechanism of electrophilic addition, illustrating how the double bond of the alkene interacts with bromine in a solvent like carbon tetrachloride (CCl₄).
Transcribed Image Text:### Exploring Bromination Mechanisms of Alkenes **Question:** Which arrow-pushing mechanism best explains the bromination of the following alkene shown below? - **Reaction:** \[ \text{MeO}C=C(\text{Me})C=O\] - Reagent: \( \text{Br}_2 \) - Solvent: \( \text{CCl}_4 \) - Product: \( \text{C}_5\text{H}_8\text{O}_2\text{Br}_2 \) **Options:** 1. **Mechanism 1:** - The double bond attacks a bromine (Br) in \( \text{Br}_2 \), forming a bromonium ion. The bromide ion then attacks a carbon, opening the bromonium ion. 2. **Mechanism 2:** - The bromine molecule adds across the double bond without forming a bromonium ion, showing a concerted mechanism. 3. **Mechanism 3:** - An initial lone pair on an oxygen atom forms a double bond, pushing electrons through the molecule and attacking \( \text{Br}_2 \), forming a cyclic structure involving bromine. 4. **Mechanism 4:** - The double bond forms a bromonium ion with one bromine, followed by the attack of the bromide ion on one of the carbons of the ion, opening the bromonium. Each mechanism involves intricate electron movements where bromine interacts with the double bond in the alkene, highlighting the importance of understanding arrow-pushing in chemical reactions. The correct answer will demonstrate the typical mechanism of electrophilic addition, illustrating how the double bond of the alkene interacts with bromine in a solvent like carbon tetrachloride (CCl₄).
### Organic Chemistry Intermediates

This section explores various organic chemistry intermediates that are commonly encountered in reactions, specifically in the context of oxymercuration.

#### Option 1
This structure involves a cyclic molecule with a positive charge on one of the interior carbon atoms. An OH (hydroxyl) group is bonded to a carbon adjacent to an HgOAc group, where Hg refers to mercury and OAc is the acetate ion. Another carbon atom is bonded to an OR group, where R represents a generic alkyl group, and a CH₃ (methyl) group.

#### Option 2
This intermediate features a cyclic molecule where one carbon has an H atom and another carbon with an OAc group. The positive charge is located on a carbon bonded to an HgOAc group. An OR group and a CH₃ group are bonded to consecutive carbon atoms.

#### Option 3
The structure demonstrates a configuration where the positive charge is on a cyclic carbon atom near an Hg group attached to an acetate ion (OAc). One carbon is bonded to a hydrogen atom and another bears an OR group and a methyl group (CH₃).

#### Option 4
This intermediate consists of a cycle with an HgOAc group attached to an interior carbon. Another carbon is bonded to an OR group, with a forward arrow indicating movement towards a syn addition across what seems to be an alkene, terminating in a CH₃ group.

These diagrams represent key steps in reaction mechanisms, focusing mainly on interactions involving mercury (Hg) in the context of oxymercuration. Understanding these intermediates is crucial for predicting the outcomes of synthetic transformations in organic chemistry.
Transcribed Image Text:### Organic Chemistry Intermediates This section explores various organic chemistry intermediates that are commonly encountered in reactions, specifically in the context of oxymercuration. #### Option 1 This structure involves a cyclic molecule with a positive charge on one of the interior carbon atoms. An OH (hydroxyl) group is bonded to a carbon adjacent to an HgOAc group, where Hg refers to mercury and OAc is the acetate ion. Another carbon atom is bonded to an OR group, where R represents a generic alkyl group, and a CH₃ (methyl) group. #### Option 2 This intermediate features a cyclic molecule where one carbon has an H atom and another carbon with an OAc group. The positive charge is located on a carbon bonded to an HgOAc group. An OR group and a CH₃ group are bonded to consecutive carbon atoms. #### Option 3 The structure demonstrates a configuration where the positive charge is on a cyclic carbon atom near an Hg group attached to an acetate ion (OAc). One carbon is bonded to a hydrogen atom and another bears an OR group and a methyl group (CH₃). #### Option 4 This intermediate consists of a cycle with an HgOAc group attached to an interior carbon. Another carbon is bonded to an OR group, with a forward arrow indicating movement towards a syn addition across what seems to be an alkene, terminating in a CH₃ group. These diagrams represent key steps in reaction mechanisms, focusing mainly on interactions involving mercury (Hg) in the context of oxymercuration. Understanding these intermediates is crucial for predicting the outcomes of synthetic transformations in organic chemistry.
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