Which of the following can give highest yield in Friedel craft reaction?

Options

A.
B.
C.
D.

Explanation

To determine which compound gives the highest yield in a Friedel-Craft reaction, we need to analyze the four compounds provided: aniline, phenol, chlorobenzene, and benzamide.

### Step-by-Step Solution:

1. **Understanding Friedel-Craft Reactions**:
- Friedel-Craft reactions include two types: alkylation and acylation.
- Both reactions are electrophilic aromatic substitutions where the electrophile is either an alkyl group or an acylium ion.
- The catalyst used is typically anhydrous aluminum chloride (AlCl3), which helps in generating the electrophile.

2. **Analyzing the Compounds**:
- **Aniline (C6H5NH2)**:
- Aniline has a lone pair of electrons on the nitrogen atom, which can interact with AlCl3.
- This interaction leads to the formation of a complex that withdraws electron density from the benzene ring, making it less reactive towards electrophiles.
- Therefore, aniline does not give a significant yield in Friedel-Craft reactions.

- **Phenol (C6H5OH)**:
- Similar to aniline, phenol has a lone pair of electrons on the oxygen atom.
- The lone pair can also coordinate with AlCl3, resulting in a complex that decreases the electron density of the benzene ring.
- Thus, phenol also does not provide a high yield in Friedel-Craft reactions.

- **Chlorobenzene (C6H5Cl)**:
- Chlorobenzene has a chlorine atom that exhibits both -I (inductive) and +M (mesomeric) effects.
- The +M effect of chlorine can donate electron density to the benzene ring, increasing its reactivity towards electrophiles.
- Therefore, chlorobenzene is expected to give a higher yield in Friedel-Craft reactions compared to aniline and phenol.

- **Benzamide (C6H5CONH2)**:
- Benzamide has a carbonyl group (C=O) which is electron-withdrawing due to resonance and inductive effects.
- This makes the benzene ring less electron-rich and less reactive towards electrophiles, resulting in a low yield in Friedel-Craft reactions.

3. **Conclusion**:
- Among the four compounds, chlorobenzene is the most reactive in Friedel-Craft reactions due to the +M effect of the chlorine atom, which enhances the electron density of the benzene ring.
- Therefore, chlorobenzene will give the highest yield in Friedel-Craft reactions.

### Final Answer:
The compound that gives the highest yield in Friedel-Craft reactions is **Chlorobenzene (C6H5Cl)**.