Which of the following nitroso compound are in dynamic equilibrium with their tautomers ?

Options

A.
B.
C.
D.

Answer

To determine which of the given nitroso compounds are in dynamic equilibrium with their tautomers, we need to analyze each compound based on the presence of alpha hydrogen atoms. Tautomerism typically involves the migration of a hydrogen atom and a shift in the position of a double bond, leading to the formation of tautomers.

### Step-by-Step Solution:

1. **Understanding Tautomerism**:
- Tautomerism is a chemical phenomenon where two or more structural isomers (tautomers) exist in dynamic equilibrium. This often involves the transfer of a hydrogen atom and a change in the position of a double bond.

2. **Identifying Alpha Hydrogen**:
- For a compound to exhibit tautomerism, it must have an alpha carbon (the carbon adjacent to the functional group) with at least one alpha hydrogen. This hydrogen is essential for the tautomeric shift.

3. **Analyzing Each Compound**:
- **Compound A**: CH3N=O (Nitroso compound)
- This compound has an alpha carbon (the carbon attached to the nitroso group) and possesses an alpha hydrogen. Therefore, it can undergo tautomerism.
- **Compound B**: CNO (Nitroso compound)
- Similar to Compound A, this compound has an alpha carbon and an alpha hydrogen, allowing for tautomerism.
- **Compound C**: (No alpha hydrogen present)
- This compound lacks an alpha hydrogen, which means it cannot undergo tautomerism.
- **Compound D**: (No alpha hydrogen present)
- Like Compound C, this compound also lacks an alpha hydrogen and cannot exhibit tautomerism.

4. **Conclusion**:
- The compounds that are in dynamic equilibrium with their tautomers are **Compound A and Compound B**. Both have alpha hydrogens and can participate in tautomeric shifts.

### Final Answer:
The nitroso compounds that are in dynamic equilibrium with their tautomers are **Compound A and Compound B**.