Which of the following is polar aprotic solvent ?

Options

A. DMSO
B. Crown ether:
C. DMG
D. All of these

Explanation

To determine which of the following is a polar aprotic solvent, we need to understand the definitions of "polar" and "aprotic."

### Step-by-step Solution:

1. **Understanding Polar Solvents**:
- A solvent is considered polar if it has a significant difference in electronegativity between its atoms, leading to a dipole moment. This means that the molecule has regions of partial positive and negative charges.

2. **Understanding Aprotic Solvents**:
- Aprotic solvents are those that do not have hydrogen atoms bonded to electronegative atoms (like oxygen or nitrogen). This means they do not have acidic protons that can participate in hydrogen bonding.

3. **Analyzing the Given Options**:
- Let's analyze the potential candidates for polar aprotic solvents:
- **DMSO (Dimethyl sulfoxide)**:
- Structure: \( \text{(CH}_3)_2\text{SO} \)
- Contains a sulfur atom double-bonded to oxygen. The oxygen is more electronegative than sulfur, creating a dipole moment. There are no hydrogen atoms bonded to electronegative atoms, making it aprotic.
- Conclusion: DMSO is a polar aprotic solvent.

- **Crown Ether**:
- Structure: A cyclic compound with ether linkages (e.g., multiple -O- groups).
- Contains electronegative oxygen atoms, creating a polar environment. Additionally, it does not have hydrogen atoms bonded to electronegative atoms.
- Conclusion: Crown ether is also a polar aprotic solvent.

- **DMG (Dimethylglyoxime)**:
- Structure: \( \text{(CH}_3)_2\text{C}(=N-OH) \)
- Contains nitrogen and oxygen, which are electronegative. The molecule has a dipole moment due to the electronegativity difference. However, it has hydroxyl (-OH) groups, which means it has hydrogen attached to an electronegative atom.
- Conclusion: DMG is not a polar aprotic solvent.

4. **Final Conclusion**:
- From the analysis, DMSO and crown ether are polar aprotic solvents, while DMG is not. Therefore, the correct answer is that both DMSO and crown ether are polar aprotic solvents.