The least electrolphilic `sp^(2)` carbon present in

Options

A.
B.
C.
D.

Answer

To determine the least electrophilic sp² carbon from the given structures, we need to analyze the effects of substituents on the electrophilicity of each carbon atom.

### Step-by-step Solution:

1. **Identify the Structures**:
We have four structures to analyze:
- Structure 1: CH₃C(=O)OCH₃
- Structure 2: CH₃C(=O)CH₃
- Structure 3: CH₃C(=O)N(CH₃)₂
- Structure 4: CH₃C(=O)C₆H₅

2. **Identify the sp² Carbons**:
In each structure, the carbon atom involved in the double bond (C=O) is the sp² carbon we are interested in.

3. **Analyze Electrophilicity**:
Electrophilicity of a carbon atom is influenced by the electron-withdrawing or electron-donating effects of substituents:
- **Structure 1**: The carbon is bonded to an oxygen (O) which is highly electronegative and exerts a strong -I (inductive) effect, making the carbon more electrophilic.
- **Structure 2**: The carbon is bonded to two methyl groups (CH₃), which exert a +I (inductive) effect, reducing the electrophilicity of the carbon.
- **Structure 3**: The carbon is bonded to a nitrogen (N) with two methyl groups. The nitrogen has a +I effect, but it is less electronegative than oxygen. However, it can also exert a weak -I effect due to its electronegativity, but the +I effect from the methyl groups will dominate.
- **Structure 4**: The carbon is bonded to a phenyl group (C₆H₅), which has a +I effect due to resonance, but it is less effective than the strong -I effect from oxygen.

4. **Determine the Least Electrophilic Carbon**:
The carbon in Structure 2 (CH₃C(=O)CH₃) is surrounded by two methyl groups, which provide electron density to the carbon. This makes it the least electrophilic sp² carbon among the options provided.

5. **Conclusion**:
Therefore, the least electrophilic sp² carbon is found in Structure 2: CH₃C(=O)CH₃.

### Final Answer:
The least electrophilic sp² carbon is in Structure 2: CH₃C(=O)CH₃.