Which of the following statements are correct?

Options

A. `1^(@), 2^(@)`, and `3^(@)` nitro compounds can be distinguished by `HNO_(2)`.
B. `1^(@)` nitro compound with `HNO(2)` gives nitrolic acid, which gives blood-red colour with base.
C. `2^(@)` nitro compound with `HNO_(2)` gives pseudo nitrole, which gives blue colour with base.
D. `3^(@)` nitro compound does not react with `HNO_(2)`.

Answer

To determine which statements about nitro compounds are correct, we will analyze each type of nitro compound (1°, 2°, and 3°) and their reactions with nitrous acid (HNO2).

### Step-by-Step Solution:

1. **Understanding Nitro Compounds**:
- Nitro compounds can be classified based on the degree of the carbon atom to which the nitro group (NO2) is attached:
- 1° (primary) nitro compounds: RCH2NO2
- 2° (secondary) nitro compounds: R2CHNO2
- 3° (tertiary) nitro compounds: R3CNO2

2. **Reaction of 1° Nitro Compounds with HNO2**:
- 1° nitro compounds have two alpha hydrogens. When they react with HNO2, they undergo a reaction to form nitrolic acid (RCH(NO2)OH).
- This compound can further react with a base (like NaOH) to give a blue solution, indicating the formation of a specific product.

3. **Reaction of 2° Nitro Compounds with HNO2**:
- 2° nitro compounds have one alpha hydrogen. They react with HNO2 to form pseudonitrile (RCRNO2).
- This compound also reacts with a base to give a blue solution, confirming the presence of a specific product.

4. **Reaction of 3° Nitro Compounds with HNO2**:
- 3° nitro compounds have no alpha hydrogens. Therefore, they do not react with HNO2.
- This means no product is formed when 3° nitro compounds are treated with HNO2.

5. **Evaluating the Statements**:
- **Statement 1**: 1°, 2°, and 3° nitro compounds can be distinguished by HNO2. **(Correct)**
- **Statement 2**: 1° nitro compounds with HNO2 give nitrolic acid and a blood red color with base. **(Correct)**
- **Statement 3**: 2° nitro compounds with HNO2 give pseudonitrile and a blue color with base. **(Correct)**
- **Statement 4**: 3° nitro compounds do not react with HNO2. **(Correct)**

6. **Conclusion**:
- All statements regarding the reactions of nitro compounds with HNO2 are correct. Therefore, the answer is that all options (A, B, C, and D) are correct.