For the electrophilic substitution reaction involving nitration, which of the following sequence regarding the rate of reaction is true ?

Options

A. `K_(C_(6)H_(6)) gt K_(C_(6)D_(6)) gt K_(C_(6)T_(6))`
B. `K_(C_(6)H_(6))lt K_(C_(6)D_(6)) lt K_(C_(6)T_(6))`
C. `K_(C_(6)H_(6))=K_(C_(6)D_(6))=K_(C_(6)T_(6))`
D. `K_(C_(6)H_(6)) gt K_(C_(6)D_(6)) lt K_(C_(6)T_(6))`

Answer

To determine the rate of the electrophilic substitution reaction involving nitration, we need to analyze the steps involved in the reaction mechanism and how different substituents on the benzene ring affect the rate of reaction.

### Step-by-Step Solution:

1. **Understanding Nitration**:
- Nitration is an electrophilic substitution reaction where a nitro group (NO₂) is introduced into an aromatic compound, typically using a mixture of concentrated nitric acid (HNO₃) and sulfuric acid (H₂SO₄).

2. **Electrophile Generation**:
- In the presence of sulfuric acid, nitric acid generates the nitronium ion (NO₂⁺), which is the active electrophile in the nitration process. This is a crucial step as the strength and stability of the electrophile will influence the reaction rate.

3. **Mechanism of Electrophilic Substitution**:
- The benzene ring acts as a nucleophile and attacks the nitronium ion. The reaction proceeds through the following steps:
- **Step 1**: The benzene ring donates a pair of electrons to the nitronium ion, forming a sigma complex (arenium ion).
- **Step 2**: The sigma complex loses a proton (H⁺) to restore aromaticity, resulting in the formation of nitrobenzene.

4. **Rate Determining Step (RDS)**:
- The rate of the reaction is determined by the first step where the benzene ring attacks the nitronium ion. This step involves the formation of a carbocation intermediate (sigma complex), which is the slowest step in the reaction mechanism.

5. **Effect of Substituents**:
- The presence of different substituents on the benzene ring can either activate or deactivate the ring towards electrophilic substitution.
- Electron-donating groups (EDGs) such as -OH or -OCH₃ increase the rate of nitration by stabilizing the carbocation intermediate.
- Electron-withdrawing groups (EWGs) such as -NO₂ or -CF₃ decrease the rate of nitration as they destabilize the carbocation intermediate.

6. **Comparing Rates**:
- When comparing the rates of nitration for different substituted benzene compounds, the following order can be established:
- Compounds with EDGs will react faster than those with no substituents or with weakly deactivating groups.
- Compounds with strong EWGs will react slower than those with no substituents or with weakly deactivating groups.

7. **Conclusion**:
- The true sequence regarding the rate of reaction for nitration can be summarized as follows:
- The presence of electron-donating groups increases the rate of nitration, while electron-withdrawing groups decrease the rate.