The rate determining step for the preparation of nitrobenzene from benzen is

Options

A. Removal of `overset(+)(N)O_(2)`
B. Removal of `overset(+)(N)O_(3)`
C. Formation of `overset(+)(N)O_(2)`
D. Formation of `overset(+)(N)O_(3)`

Answer

To determine the rate determining step (RDS) for the preparation of nitrobenzene from benzene, we need to analyze the nitration reaction mechanism. Here’s a step-by-step breakdown of the process:

### Step 1: Understanding the Reaction
The reaction involves the nitration of benzene, which is carried out using a mixture of concentrated nitric acid (HNO3) and concentrated sulfuric acid (H2SO4). The overall reaction can be represented as:
\[ \text{C}_6\text{H}_6 + \text{HNO}_3 \xrightarrow{\text{H}_2\text{SO}_4} \text{C}_6\text{H}_5\text{NO}_2 + \text{H}_2\text{O} \]

### Step 2: Formation of the Electrophile
In the presence of sulfuric acid, nitric acid generates the nitronium ion (\(\text{NO}_2^+\)), which is the active electrophile in the nitration process. The formation of this electrophile is crucial as it initiates the reaction with benzene.

### Step 3: Identifying the Rate Determining Step
The rate determining step in a reaction is the slowest step that controls the overall rate of the reaction. In this case, the generation of the nitronium ion (\(\text{NO}_2^+\)) from the reaction of nitric acid and sulfuric acid is the slowest step. This step involves the formation of a stable electrophile, which is essential for the subsequent electrophilic aromatic substitution.

### Step 4: Mechanism of the Reaction
1. **Protonation of Nitric Acid**:
\[ \text{HNO}_3 + \text{H}_2\text{SO}_4 \rightarrow \text{NO}_2^+ + \text{HSO}_4^- + \text{H}_2\text{O} \]

2. **Electrophilic Attack**: The nitronium ion (\(\text{NO}_2^+\)) then attacks the benzene ring, leading to the formation of the sigma complex (arenium ion).

3. **Deprotonation**: Finally, the sigma complex loses a proton to regenerate the aromatic system, yielding nitrobenzene.

### Conclusion
The rate determining step (RDS) for the preparation of nitrobenzene from benzene is the formation of the nitronium ion (\(\text{NO}_2^+\)) from nitric acid and sulfuric acid.

### Answer
The rate determining step for the preparation of nitrobenzene from benzene is the formation of the nitronium ion (\(\text{NO}_2^+\)).

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