Which compound amongst the following is nitrated with most difficulty ?

Options

A. nitrobenzene
B. m-dinitrobenzene
C. phenol
D. quinol

Answer

To determine which compound amongst the given options is nitrated with the most difficulty, we need to analyze the electron density of each compound. Nitration is an electrophilic substitution reaction that requires a certain level of electron density to facilitate the attack of the nitronium ion (NO₂⁺).

### Step-by-Step Solution:

1. **Identify the Compounds**: The compounds provided are:
- A) Nitrobenzene
- B) Metadinitrobenzene
- C) Phenol
- D) Quinol

2. **Draw the Structures**:
- **Nitrobenzene**: C₆H₅NO₂ (a benzene ring with one nitro group)
- **Metadinitrobenzene**: C₆H₃(NO₂)₂ (a benzene ring with two nitro groups in the meta position)
- **Phenol**: C₆H₅OH (a benzene ring with one hydroxyl group)
- **Quinol**: C₆H₄(OH)₂ (a benzene ring with two hydroxyl groups)

3. **Analyze Electron Density**:
- **Nitrobenzene**: The nitro group is an electron-withdrawing group, which decreases the electron density of the benzene ring, making it less reactive towards electrophiles.
- **Metadinitrobenzene**: This compound has two nitro groups, both of which are electron-withdrawing. The presence of two nitro groups significantly reduces the electron density even more than in nitrobenzene.
- **Phenol**: The hydroxyl group (–OH) is an electron-donating group, which increases the electron density of the benzene ring, making it more reactive towards electrophiles.
- **Quinol**: Similar to phenol, quinol has hydroxyl groups that increase electron density, making it more reactive.

4. **Compare Reactivity**:
- The compound with the highest electron density (phenol and quinol) will undergo nitration more easily.
- Nitrobenzene has lower electron density than phenol and quinol but is still more reactive than metadinitrobenzene.
- Metadinitrobenzene, with two electron-withdrawing nitro groups, has the lowest electron density and is therefore the most difficult to nitrate.

5. **Conclusion**: Based on the analysis, the compound that is nitrated with the most difficulty is **Metadinitrobenzene (Option B)**.

### Final Answer:
**Metadinitrobenzene (Option B)** is the compound that is nitrated with the most difficulty.