Which of the following compounds is most reactive in electrophilic aromatic substitution?

Options

A.
B.
C.
D.

Answer

To determine which compound is most reactive in electrophilic aromatic substitution, we need to analyze the substituents attached to the aromatic ring in each compound. The reactivity in electrophilic aromatic substitution depends on the electron density of the aromatic ring, which is influenced by the substituents.

### Step-by-Step Solution:

1. **Identify the Compounds**: Let's assume we have four compounds:
- Compound 1: Phenol (C6H5OH)
- Compound 2: Nitrobenzene (C6H5NO2)
- Compound 3: Chlorobenzene (C6H5Cl)
- Compound 4: Anisole (C6H5OCH3)

2. **Analyze the Effects of Substituents**:
- **Phenol (C6H5OH)**: The hydroxyl group (-OH) has a +R (resonance) effect, which increases the electron density on the aromatic ring, particularly at the ortho and para positions. This makes phenol very reactive towards electrophiles.

- **Nitrobenzene (C6H5NO2)**: The nitro group (-NO2) is a strong -M (minus mesomeric) and -I (inductive) effect group. It pulls electron density away from the aromatic ring, making it less reactive towards electrophilic substitution.

- **Chlorobenzene (C6H5Cl)**: The chlorine atom has a +R effect (due to resonance) but also exhibits a -I effect (due to inductive withdrawal). The overall effect is a slight increase in electron density, but not as significant as in phenol.

- **Anisole (C6H5OCH3)**: The methoxy group (-OCH3) also has a +R effect, which increases the electron density on the ring, making it more reactive than chlorobenzene but less reactive than phenol.

3. **Compare Reactivity**:
- Phenol has the highest electron density due to the -OH group, making it the most reactive in electrophilic aromatic substitution.
- Anisole is also reactive but less so than phenol.
- Chlorobenzene has moderate reactivity due to the opposing effects of chlorine.
- Nitrobenzene is the least reactive due to the strong electron-withdrawing nature of the nitro group.

4. **Conclusion**: Based on the analysis, **Phenol (C6H5OH)** is the most reactive compound in electrophilic aromatic substitution.