Which of the following scheme is the first step in the following Grignard reaction? + I. BrMg I. BrMg + II. :BrMg IV. :BrMg の 參 bo e 公

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### Grignard Reaction: First Step Identification

**Question:**
Which of the following schemes is the first step in the following Grignard reaction?

**Schemes:**

1. **Scheme I:**
   - The scheme depicts a Grignard reagent (BrMg) approaching the carbonyl group of acetone. The reaction arrow indicates the movement of electrons from the carbon atom of the Grignard reagent (bearing a partial negative charge) towards the carbon atom of the carbonyl group, suggesting the formation of a new carbon-carbon bond. 

2. **Scheme II:**
   - In this scheme, the carbonyl oxygen's lone pair electrons are suggested to attack the magnesium of the Grignard reagent (BrMg). The electrons from the carbonyl carbon bond shift, suggesting a different mechanism compared to Scheme I.

3. **Scheme III:**
   - This scheme illustrates the lone pair of electrons on the oxygen of the carbonyl group forming a bond with the magnesium of the Grignard reagent (BrMg). The arrows and notations suggest a nucleophilic attack from the opposite direction to Scheme II.

4. **Scheme IV:**
   - Similar to Scheme II, this scheme indicates the lone pair of electrons on the carbonyl oxygen attacking the magnesium atom from BrMg. However, the positioning and resultant movement of electrons are slightly different.

**Explanation of Graphs/Diagrams:**
- Each scheme represents potential mechanisms for the initial step in the Grignard reaction involving a carbonyl compound (acetone) and a Grignard reagent (BrMg).
- The arrows within each diagram demonstrate the flow of electron pairs and indicate which atoms are involved in bond formation or breaking.
- The dotted areas represent electron lone pairs on oxygen atoms which are capable of initiating nucleophilic or electrophilic attacks.

**Objective:**
Understand the nature and direction of electron flow in Grignard reagent's interaction with a carbonyl compound to predict the correct initial mechanistic step of the reaction.

By analyzing the schemes, learners might understand the correct mechanistic step by focusing on the nucleophilicity of the carbonyl oxygen and the electrophilicity of the Grignard reagent.
Transcribed Image Text:### Grignard Reaction: First Step Identification **Question:** Which of the following schemes is the first step in the following Grignard reaction? **Schemes:** 1. **Scheme I:** - The scheme depicts a Grignard reagent (BrMg) approaching the carbonyl group of acetone. The reaction arrow indicates the movement of electrons from the carbon atom of the Grignard reagent (bearing a partial negative charge) towards the carbon atom of the carbonyl group, suggesting the formation of a new carbon-carbon bond. 2. **Scheme II:** - In this scheme, the carbonyl oxygen's lone pair electrons are suggested to attack the magnesium of the Grignard reagent (BrMg). The electrons from the carbonyl carbon bond shift, suggesting a different mechanism compared to Scheme I. 3. **Scheme III:** - This scheme illustrates the lone pair of electrons on the oxygen of the carbonyl group forming a bond with the magnesium of the Grignard reagent (BrMg). The arrows and notations suggest a nucleophilic attack from the opposite direction to Scheme II. 4. **Scheme IV:** - Similar to Scheme II, this scheme indicates the lone pair of electrons on the carbonyl oxygen attacking the magnesium atom from BrMg. However, the positioning and resultant movement of electrons are slightly different. **Explanation of Graphs/Diagrams:** - Each scheme represents potential mechanisms for the initial step in the Grignard reaction involving a carbonyl compound (acetone) and a Grignard reagent (BrMg). - The arrows within each diagram demonstrate the flow of electron pairs and indicate which atoms are involved in bond formation or breaking. - The dotted areas represent electron lone pairs on oxygen atoms which are capable of initiating nucleophilic or electrophilic attacks. **Objective:** Understand the nature and direction of electron flow in Grignard reagent's interaction with a carbonyl compound to predict the correct initial mechanistic step of the reaction. By analyzing the schemes, learners might understand the correct mechanistic step by focusing on the nucleophilicity of the carbonyl oxygen and the electrophilicity of the Grignard reagent.
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