Nitrobenzene on reaction with conc. `(HNO_3)/(H_2SO_4)` at `80-100^@C` forms which one of the following products?

Options

A. 1,3-dinitrobenzene
B. 1,4-Dinitrobenzene
C. 1,2,4-Trinitrobenzene
D. 1,2-dinitrobenzene

Explanation

To solve the question regarding the reaction of nitrobenzene with concentrated nitric acid (HNO3) and sulfuric acid (H2SO4) at 80-100°C, we will follow these steps:

### Step 1: Identify the Reaction Type
The reaction in question is a nitration reaction, which is an electrophilic aromatic substitution reaction. In this case, we are nitrating nitrobenzene.

**Hint:** Remember that nitration involves the substitution of a hydrogen atom on the aromatic ring with a nitro group (NO2).

### Step 2: Understand the Electrophile
In nitration, the electrophile is the nitronium ion (NO2+), which is generated from the reaction of concentrated HNO3 and H2SO4. This ion is what will attack the aromatic ring of nitrobenzene.

**Hint:** The nitronium ion (NO2+) is the active species that will attack the benzene ring.

### Step 3: Analyze the Substituents on Nitrobenzene
Nitrobenzene already contains a nitro group (-NO2) attached to the benzene ring. This group is a deactivating group due to its -I (inductive) and -R (resonance) effects, which reduce the reactivity of the aromatic ring towards further electrophilic substitution. Additionally, it is a meta-directing group.

**Hint:** Identify how existing substituents influence the position of new substituents in electrophilic aromatic substitution.

### Step 4: Determine the Position of Electrophilic Attack
Since the nitro group is meta-directing, the incoming nitronium ion (NO2+) will preferentially attack the meta position relative to the existing nitro group. The positions on the benzene ring can be labeled as follows:
- Ortho position (1,2)
- Meta position (1,3)
- Para position (1,4)

Given that the nitro group directs the incoming electrophile to the meta position, the nitronium ion will attack the carbon that is meta to the existing nitro group.

**Hint:** Visualize the benzene ring and mark the positions to see where the new nitro group will be added.

### Step 5: Write the Product Structure
After the electrophilic attack, the product formed will have two nitro groups on the benzene ring. The positions of these groups will be at the 1 and 3 positions, leading to the formation of 1,3-dinitrobenzene.

**Hint:** Draw the structure of the product to confirm that it has two nitro groups at the correct positions.

### Conclusion
The final product of the reaction of nitrobenzene with concentrated HNO3 and H2SO4 at 80-100°C is 1,3-dinitrobenzene.

**Final Answer:** The product formed is 1,3-dinitrobenzene (option A).