Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is

Options

A. `CH_(3)COCl`
B. `CH_(3)COOCH_(3)`
C. `CH_(3)CONH_(2)`
D. `CH_(3)COOCOCH_(3)`

Explanation

To determine which compound is most susceptible to nucleophilic attack at the carbonyl group, we need to analyze the given compounds based on the electronic effects exerted by their substituents on the carbonyl carbon. The carbonyl group (C=O) has a carbon atom that carries a partial positive charge due to the electronegativity difference between carbon and oxygen. Nucleophiles are attracted to this partial positive charge.

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds given are:
- Acetyl chloride (CH3C(=O)Cl)
- Acetaldehyde (CH3C(=O)H)
- Acetamide (CH3C(=O)NH2)
- Acetic acid (CH3C(=O)OH)

2. **Analyze Electron-Withdrawing and Electron-Donating Effects**:
- **Acetyl Chloride (CH3C(=O)Cl)**: The chlorine atom is a strong electron-withdrawing group due to its -I (inductive) effect. This increases the partial positive charge on the carbonyl carbon, making it more susceptible to nucleophilic attack.
- **Acetaldehyde (CH3C(=O)H)**: The hydrogen atom does not have a significant electron-withdrawing effect. Thus, the carbonyl carbon is less positive compared to acetyl chloride.
- **Acetamide (CH3C(=O)NH2)**: The amine group (NH2) has a +M (mesomeric) effect, which donates electron density to the carbonyl carbon, reducing its susceptibility to nucleophilic attack.
- **Acetic Acid (CH3C(=O)OH)**: The hydroxyl group (OH) also has a +M effect, which decreases the positive charge on the carbonyl carbon, making it less susceptible to nucleophilic attack.

3. **Compare the Susceptibility**:
- Acetyl chloride has the strongest electron-withdrawing effect due to chlorine, leading to a higher positive charge on the carbonyl carbon.
- Acetaldehyde has a moderate susceptibility due to the lack of strong electron-withdrawing groups.
- Acetamide and acetic acid are the least susceptible due to the electron-donating effects of the NH2 and OH groups.

4. **Conclusion**: Among the given compounds, acetyl chloride (CH3C(=O)Cl) is the most susceptible to nucleophilic attack at the carbonyl group due to the strong electron-withdrawing effect of the chlorine atom.

### Final Answer:
The most susceptible compound to nucleophilic attack at the carbonyl group is **Acetyl Chloride (CH3C(=O)Cl)**.