Which of the following can show conformational isomerism:

Options

A. `CD_(3)-H`
B. `CH_(2)(OH)CH_(2)OH`
C. `NH_(3)`
D. All of these

Answer

To determine which of the given compounds can show conformational isomerism, we need to analyze each option based on the ability to rotate around single bonds and the resulting different spatial arrangements.

### Step-by-Step Solution:

1. **Understanding Conformational Isomerism**:
- Conformational isomerism occurs due to rotation around single bonds, leading to different spatial arrangements of atoms in a molecule. This is significant when there are distinct groups attached to the carbon atoms involved in the rotation.

2. **Analyzing Option 1**:
- The first compound has a carbon atom bonded to three deuterium atoms and one hydrogen atom.
- Since three of the substituents (deuterium) are identical, rotation around the carbon-carbon bond will not lead to any significant change in the energy or arrangement of the molecule.
- **Conclusion**: This compound does not show conformational isomerism.

3. **Analyzing Option 2**:
- The second compound consists of two carbon atoms connected by a single bond, with hydroxyl (OH) groups and hydrogen atoms attached.
- Here, the rotation around the carbon-carbon bond can lead to different arrangements of the OH groups relative to each other (e.g., staggered vs. eclipsed conformations).
- The energy of the molecule will vary depending on the spatial arrangement of these groups.
- **Conclusion**: This compound can show conformational isomerism.

4. **Analyzing Option 3**:
- The third option is ammonia (NH3), which has a nitrogen atom bonded to three hydrogen atoms and a lone pair.
- The presence of the lone pair and identical hydrogen atoms means that rotation does not lead to different conformations that significantly change the spatial arrangement or energy.
- **Conclusion**: This compound does not show conformational isomerism.

5. **Final Answer**:
- Based on the analysis, the only compound that can show conformational isomerism is the second compound.