Hyperconjugation observed in

Options

A.
B. `overset(.)CPh_(3)`
C.
D.

Answer

To determine which molecules exhibit hyperconjugation, we need to understand the concept of hyperconjugation and identify the presence of alpha hydrogen atoms in the given options. Here is a step-by-step solution:

### Step 1: Understand Hyperconjugation
Hyperconjugation is the interaction between the electrons in a sigma bond (usually C-H or C-C) and an adjacent empty or partially filled p-orbital or pi-orbital. This interaction leads to the stabilization of the molecule.

**Hint:** Remember that hyperconjugation involves sigma bonds and adjacent empty or partially filled orbitals.

### Step 2: Identify Alpha Hydrogen Atoms
For hyperconjugation to occur, the molecule must have alpha hydrogen atoms. Alpha hydrogens are those hydrogen atoms that are attached to the carbon atom adjacent to a double bond, positive charge, free radical, or negative charge.

**Hint:** Look for hydrogen atoms attached to carbons next to double bonds or charged species.

### Step 3: Analyze Each Option
Now, we will analyze each option to see if it contains alpha hydrogen atoms.

1. **Option 1:** The molecule has no alpha hydrogens because all hydrogens are replaced by methyl groups. Thus, it cannot exhibit hyperconjugation.

**Hint:** Check for the presence of hydrogen atoms on the carbon adjacent to the reactive site.

2. **Option 2:** This molecule has a free radical. The adjacent carbon has one hydrogen atom, which is an alpha hydrogen. Therefore, this molecule can exhibit hyperconjugation.

**Hint:** Identify the free radical and check the adjacent carbon for hydrogen atoms.

3. **Option 3:** Similar to option 2, this molecule has a free radical with one hydrogen atom on the adjacent carbon. Hence, it can exhibit hyperconjugation.

**Hint:** Look for the free radical and count the hydrogen atoms on adjacent carbons.

4. **Option 4:** This molecule has no alpha hydrogens as all valencies of the carbon are satisfied with other groups. Thus, it cannot exhibit hyperconjugation.

**Hint:** Ensure that the carbon adjacent to the reactive site has available hydrogen atoms.

### Conclusion
Based on the analysis:
- **Option 2 and Option 3** show hyperconjugation due to the presence of alpha hydrogen atoms.
- **Option 1 and Option 4** do not show hyperconjugation as they lack alpha hydrogen atoms.

**Final Answer:** Hyperconjugation is observed in Option 2 and Option 3.