Which will not give a white ppt with ` "AgNO"_(3)`?

Options

A. Allyl chloride
B. Vinyl chloride
C. Chlorobenzene
D. Both (2) and (3)

Answer

To determine which compound will not give a white precipitate with AgNO₃, we need to analyze the reactivity of the halogen in each compound. The formation of a white precipitate (AgCl) occurs when a halogen (Cl⁻) is released and reacts with Ag⁺ ions. Let's evaluate the options step by step.

### Step 1: Analyze Allyl Chloride
1. **Structure**: Allyl chloride has the structure CH₂=CH-CH₂Cl.
2. **Reactivity**: The chlorine atom is attached to the carbon adjacent to a double bond (allylic position).
3. **Mechanism**: When allyl chloride reacts with AgNO₃, the chlorine can leave as Cl⁻, forming a stable allylic carbocation (CH₂=CH-CH₂⁺).
4. **Precipitate Formation**: The Cl⁻ can then react with Ag⁺ to form AgCl, which is a white precipitate.

**Conclusion**: Allyl chloride will give a white precipitate with AgNO₃.

### Step 2: Analyze Vinyl Chloride
1. **Structure**: Vinyl chloride has the structure CH₂=CHCl.
2. **Reactivity**: The chlorine atom is attached directly to a carbon that is part of a double bond (vinylic position).
3. **Mechanism**: When vinyl chloride reacts, the Cl atom cannot leave easily because the resulting carbocation (CH₂=CH⁺) is unstable.
4. **Precipitate Formation**: Since the carbocation is not stable, Cl⁻ will not be formed, and thus it cannot react with Ag⁺ to form AgCl.

**Conclusion**: Vinyl chloride will **not** give a white precipitate with AgNO₃.

### Step 3: Analyze Chlorobenzene
1. **Structure**: Chlorobenzene has the structure C₆H₅Cl.
2. **Reactivity**: The chlorine atom is bonded to a benzene ring, which is a stable aromatic system.
3. **Mechanism**: The C-Cl bond in chlorobenzene is strong and does not undergo nucleophilic substitution easily. The chlorine does not leave as Cl⁻.
4. **Precipitate Formation**: Since Cl⁻ is not formed, it cannot react with Ag⁺ to produce AgCl.

**Conclusion**: Chlorobenzene will also **not** give a white precipitate with AgNO₃.

### Final Answer
The compounds that will not give a white precipitate with AgNO₃ are **Vinyl Chloride and Chlorobenzene**. Therefore, the correct answer is option **D (both 2 and 3)**.

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