Which of the following reagent will not be able to produce acetyl chloride by its reaction with acetic acid?

Options

A. `PCl_(5)`
B. `SOCl_(2)//Py`
C. `PCl_(3)`
D. `Cl_(2)`

Answer

To determine which reagent will not produce acetyl chloride when reacted with acetic acid, we need to analyze the reactivity of each reagent with acetic acid.

### Step-by-Step Solution:

1. **Identify the Structure of Acetic Acid:**
- Acetic acid has the formula CH₃COOH. It consists of a methyl group (CH₃) attached to a carboxylic acid group (COOH).

2. **Understand the Desired Reaction:**
- The goal is to convert acetic acid (CH₃COOH) into acetyl chloride (CH₃COCl). This involves replacing the hydroxyl group (OH) in acetic acid with a chlorine atom (Cl).

3. **Analyze the Reagents:**
- We need to evaluate each of the given reagents to see if they can facilitate the conversion of acetic acid to acetyl chloride.

4. **Reagent 1: Phosphorus Pentachloride (PCl₅):**
- PCl₅ is a strong chlorinating agent and can convert acetic acid to acetyl chloride by replacing the OH group with Cl.
- **Conclusion:** PCl₅ can produce acetyl chloride.

5. **Reagent 2: Thionyl Chloride (SOCl₂):**
- Thionyl chloride is also a strong chlorinating agent. It reacts with carboxylic acids to produce acyl chlorides, including acetyl chloride.
- **Conclusion:** SOCl₂ can produce acetyl chloride.

6. **Reagent 3: Phosphorus Trichloride (PCl₃):**
- PCl₃ can also convert acetic acid to acetyl chloride by replacing the OH group with Cl.
- **Conclusion:** PCl₃ can produce acetyl chloride.

7. **Reagent 4: Chlorine Gas (Cl₂):**
- Chlorine gas does not directly replace the OH group in acetic acid. Instead, it can lead to the formation of alpha-chlorinated acetic acid (CH₂ClCOOH) without converting the carboxylic acid to an acyl chloride.
- **Conclusion:** Cl₂ cannot produce acetyl chloride.

8. **Final Answer:**
- The reagent that will not be able to produce acetyl chloride by its reaction with acetic acid is **Chlorine Gas (Cl₂)**.

### Summary:
Out of the given options, **Chlorine Gas (Cl₂)** is the reagent that will not produce acetyl chloride when reacted with acetic acid.

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