Which of the given species cannot be used in Friedel Craft's reactions ?

Options

A. `AlCl_3`
B. `FeCl_3`
C. `FeBr_2`
D. `NaCl`

Answer

To determine which species cannot be used in Friedel-Crafts reactions, we need to analyze the nature of the given species and their ability to act as Lewis acids. Friedel-Crafts reactions typically require a strong Lewis acid to facilitate the electrophilic aromatic substitution.

### Step-by-Step Solution:

1. **Understand Friedel-Crafts Reactions**:
- Friedel-Crafts reactions involve the alkylation or acylation of aromatic compounds. They require a Lewis acid catalyst to generate a more reactive electrophile.

2. **Identify Lewis Acids**:
- Lewis acids are electron-deficient species that can accept an electron pair. Common Lewis acids used in Friedel-Crafts reactions include AlCl₃, FeCl₃, and certain metal cations.

3. **Evaluate Given Species**:
- The question provides several species (A, B, C, D) and asks which one cannot be used in Friedel-Crafts reactions.
- We need to consider the nature of each species and whether they can act as Lewis acids.

4. **Consider Inert Gas Configuration**:
- Cations like Na⁺ and K⁺ have an inert gas configuration and do not have a strong tendency to accept electrons. Therefore, they do not act as Lewis acids.

5. **Identify the Correct Answer**:
- If one of the options is NaCl, it cannot be used in Friedel-Crafts reactions because Na⁺ does not act as a Lewis acid. Thus, the correct answer is option D (NaCl).

### Final Answer:
The species that cannot be used in Friedel-Crafts reactions is **NaCl** (Option D).

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