Which of the following reacts with nitrous acid

Options

A. Acetamide
B. 2-Nitrobutane
C. 2-methyl-2-nitropropane
D. Diethylamine

Explanation

To determine which of the given compounds reacts with nitrous acid (HON), we need to analyze each compound for the presence of alpha-hydrogens. Compounds that have alpha-hydrogens can undergo a reaction with nitrous acid, while those that do not will not react.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Compound A: Acetamide (CH3CONH2)
- Compound B: 2-Nitrobutene (C4H7NO2)
- Compound C: 2-Methyl-2-nitropropene (C5H9NO2)
- Compound D: Dimethylamine ((CH3)2NH)

2. **Check for Alpha-Hydrogens**:
- **Acetamide (A)**:
- Structure: CH3CONH2
- Alpha-hydrogens: Yes (the methyl group has three alpha-hydrogens).
- **2-Nitrobutene (B)**:
- Structure: C4H7NO2
- Alpha-hydrogens: Yes (the carbon adjacent to the nitro group has hydrogens).
- **2-Methyl-2-nitropropene (C)**:
- Structure: C5H9NO2
- Alpha-hydrogens: No (the carbon with the nitro group is tertiary and has no alpha-hydrogens).
- **Dimethylamine (D)**:
- Structure: (CH3)2NH
- Alpha-hydrogens: Yes (the methyl groups have hydrogens).

3. **Determine Reactivity with Nitrous Acid**:
- **Acetamide (A)**: Reacts with nitrous acid due to the presence of alpha-hydrogens.
- **2-Nitrobutene (B)**: Reacts with nitrous acid due to the presence of alpha-hydrogens.
- **2-Methyl-2-nitropropene (C)**: Does not react with nitrous acid due to the absence of alpha-hydrogens.
- **Dimethylamine (D)**: Reacts with nitrous acid due to the presence of alpha-hydrogens.

4. **Conclusion**:
- The compounds that react with nitrous acid are Acetamide (A), 2-Nitrobutene (B), and Dimethylamine (D).
- The compound that does not react is 2-Methyl-2-nitropropene (C).

### Final Answer:
The compounds that react with nitrous acid are:
- Acetamide (A)
- 2-Nitrobutene (B)
- Dimethylamine (D)

The compound that does not react is:
- 2-Methyl-2-nitropropene (C).