Torsion strain is the repulsive interaction between

Options

A. Electron cloud of two bonds
B. Electron cloud of two `sigma`-bonds
C. Electron cloud of two pie-bonds
D. Electron cloud of two `sigma`-bonds on adjacent atoms

Answer

To solve the question regarding torsion strain, we need to understand what torsion strain is and how it relates to the interactions between electron clouds of bonds in a molecule.

### Step-by-Step Solution:

1. **Understanding Torsion Strain**: Torsion strain, also known as torsional strain, occurs when there is a repulsive interaction between the electron clouds of bonds in a molecule. This strain is particularly significant when the bonds are in a staggered conformation versus an eclipsed conformation.

2. **Identifying the Bonds**: In the context of the question, we need to identify which bonds are involved in torsion strain. The options provided are:
- Electron clouds of two bonds
- Electron clouds of two sigma bonds
- Electron clouds of two pi bonds
- Electron clouds of two sigma bonds on adjacent atoms

3. **Analyzing the Options**:
- **Electron clouds of two bonds**: This is too vague as it does not specify the type of bonds.
- **Electron clouds of two sigma bonds**: This could be a possibility, but it does not specify their position relative to each other.
- **Electron clouds of two pi bonds**: Pi bonds generally do not contribute to torsion strain as they are not involved in the same way as sigma bonds.
- **Electron clouds of two sigma bonds on adjacent atoms**: This option specifies that the sigma bonds are on adjacent atoms, which is crucial for torsion strain.

4. **Conclusion**: Based on the analysis, the correct answer is **Option D: electron clouds of two sigma bonds on adjacent atoms**. This is because torsion strain arises when the sigma bonds of adjacent atoms are aligned in such a way that their electron clouds repel each other, particularly in an eclipsed conformation.

### Final Answer:
Torsion strain is the repulsive interaction between **electron clouds of two sigma bonds on adjacent atoms**.