Which of the following on reactions with nitrous acid, followed by treatment with `NaOH` produces a blue coluration?

Options

A. `RCH_(2)NO_(2)`
B. `R_(3)CNO_(2)`
C. `R_(2)CHNO_(2)`
D. `PhCNO_(2)`

Answer

To solve the question regarding which compound reacts with nitrous acid followed by treatment with NaOH to produce a blue coloration, we can follow these steps:

### Step 1: Understand the Reaction with Nitrous Acid
- **Nitrous acid (HNO2)** reacts differently with primary, secondary, and tertiary nitroalkanes.
- Primary nitroalkanes typically yield a red color upon reaction with nitrous acid, while secondary nitroalkanes yield a blue color.

### Step 2: Identify the Types of Nitroalkanes
- **Primary Nitroalkanes (1°)**: These have the structure RCH2NO2.
- **Secondary Nitroalkanes (2°)**: These have the structure R2CHNO2.
- **Tertiary Nitroalkanes (3°)**: These have the structure R3CNO2 and do not react with nitrous acid due to the absence of an alpha hydrogen.

### Step 3: Analyze the Reaction Products
- When a **secondary nitroalkane** reacts with nitrous acid, it forms a nitroso compound (R2C=NO) which gives a blue color when treated with NaOH.
- In contrast, primary nitroalkanes form a different product that results in a red color upon treatment with NaOH.

### Step 4: Conclusion
- Based on the above analysis, the compound that will produce a blue coloration after reacting with nitrous acid and being treated with NaOH is a **secondary nitroalkane**.

### Final Answer
The answer to the question is that **secondary nitroalkanes** produce a blue coloration when reacted with nitrous acid followed by treatment with NaOH.

---