Which of the following cannot be acetylated with `CH_3 COCl//Py` ?

Options

A. `MeCOOH`
B. `CH_3 NH_2`
C.
D.

Explanation

To determine which of the given compounds cannot be acetylated with acetyl chloride (CH3COCl) in the presence of pyridine, we will analyze each option based on their functional groups and reactivity.

### Step-by-Step Solution:

1. **Understanding Acetylation**:
Acetylation is a chemical reaction where an acetyl group (CH3CO-) is introduced into a compound. This reaction typically occurs with compounds that have nucleophilic sites, such as alcohols and amines.

2. **Analyzing Each Option**:
- **Option A: Acetic Acid (CH3COOH)**
Acetic acid has a carboxylic acid functional group. In the presence of acetyl chloride, it does not react because the carboxylic acid group is not nucleophilic enough to undergo acetylation. Therefore, acetic acid cannot be acetylated.

- **Option B: Primary Amine (RNH2)**
Primary amines contain an amino group (NH2), which is nucleophilic. When treated with acetyl chloride, the amino group will react and form an acetamide. Thus, this compound can be acetylated.

- **Option C: Ortho-Hydroxybenzoic Acid (Salicylic Acid)**
This compound has both a carboxylic acid and a hydroxyl group. The hydroxyl group is nucleophilic and can react with acetyl chloride to form an ester. Therefore, this compound can also be acetylated.

- **Option D: Alcohol with a Phenyl Group**
This compound has an alcohol functional group (-OH), which is also nucleophilic. It can react with acetyl chloride to form an ester. Hence, this compound can be acetylated as well.

3. **Conclusion**:
After analyzing all options, we find that only **Option A (Acetic Acid)** cannot be acetylated with CH3COCl in the presence of pyridine. The other options (B, C, and D) can undergo acetylation.

### Final Answer:
**Option A: Acetic Acid (CH3COOH)** cannot be acetylated with CH3COCl in the presence of pyridine.