The major product formed on nitration of N, N - dimethylaniline with conc. `H_2SO_4,NHO_3` mixture is

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Answer

To determine the major product formed from the nitration of N,N-dimethylaniline with a concentrated mixture of sulfuric acid (H₂SO₄) and nitric acid (HNO₃), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure of N,N-Dimethylaniline**:
- N,N-dimethylaniline is an aniline derivative where two methyl groups are attached to the nitrogen atom. The structure can be represented as:
\[ \text{C}_6\text{H}_5\text{N}(\text{CH}_3)_2 \]
- The nitrogen atom has a lone pair of electrons that can donate electron density to the aromatic ring.

2. **Understand the Nitration Reaction**:
- Nitration involves the introduction of a nitro group (NO₂) into the aromatic ring. The nitrating agent in this case is the mixture of concentrated H₂SO₄ and HNO₃, which generates the electrophile \( \text{NO}_2^+ \).

3. **Effect of Electron-Donating Groups**:
- The two methyl groups attached to the nitrogen are electron-donating groups (+M effect), which increase the electron density at the ortho and para positions of the aromatic ring. However, under strong acidic conditions, the lone pair of the nitrogen is protonated, making it a deactivating group.

4. **Protonation of the Amino Group**:
- In concentrated acidic conditions, the nitrogen atom in N,N-dimethylaniline gets protonated, losing its ability to donate electron density effectively to the ring. This results in the nitrogen acting as a deactivating group.

5. **Nitration Position Preference**:
- Due to the deactivating effect of the protonated nitrogen, the electron density at the ortho and para positions decreases. The meta position, however, retains some electron density because it is less affected by the deactivating group.
- Therefore, the nitro group will preferentially attack the meta position.

6. **Final Product**:
- The major product formed from the nitration of N,N-dimethylaniline under these conditions will be 3-nitro-N,N-dimethylaniline, where the nitro group is located at the meta position relative to the dimethylamino group.

### Conclusion:
The major product formed from the nitration of N,N-dimethylaniline with concentrated H₂SO₄ and HNO₃ is **3-nitro-N,N-dimethylaniline**.