Which of the following is used as a solvent in the Friedel-Crafts
reaction :-

Options

A. Toluene
B. Nitrobenzene
C. Benzene
D. Aniline

Answer

### Step-by-Step Solution:

1. **Understanding Friedel-Crafts Reaction**:
Friedel-Crafts reactions are a type of electrophilic substitution reaction that involves the alkylation or acylation of benzene or its derivatives. In these reactions, a benzene ring reacts with an alkyl halide or an acyl halide in the presence of a Lewis acid catalyst.

2. **Identifying the Role of Solvent**:
The solvent in a Friedel-Crafts reaction must not interfere with the reaction mechanism. It should ideally stabilize the reactants and facilitate the reaction without participating in it.

3. **Common Solvents in Friedel-Crafts Reactions**:
While several solvents can be used, nitrobenzene is often highlighted as a preferred solvent. This is because it has a strong electron-withdrawing nitro group (NO2), which makes it a good solvent for electrophilic substitution reactions.

4. **Why Nitrobenzene?**:
Nitrobenzene acts as a deactivator for electrophilic substitution due to its electron-withdrawing nature. This means that it lowers the electron density on the benzene ring, making it less reactive towards electrophiles. This property allows the reaction to proceed without the solvent itself being attacked by the electrophile.

5. **Conclusion**:
Based on the above points, the solvent used in the Friedel-Crafts reaction is nitrobenzene. Therefore, the correct answer is option B: Nitrobenzene.