Electronegativity of carbon atoms depends upon their state of hybridisation. In which of the following compounds, the carbon marked with asterisk is most electronegative?

Options

A. `CH_(3)-CH_(2)-CH_(2)-CH_(3)`
B. `CH_(3)-overset(***)(C)H=CH-CH_(3)`
C. `CH_(3)-CH_(2)-C-=overset(***)(C)H`
D. `CH_(3)-CH_(2)-CH=overset(***)(C)H_(2)`

Explanation

To determine which carbon atom marked with an asterisk is the most electronegative based on its hybridization state, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Electronegativity and Hybridization**:
Electronegativity of carbon is influenced by its hybridization state. The more s-character in the hybridization, the more electronegative the carbon atom. The hybridization states and their corresponding s-character are:
- sp hybridization: 50% s-character
- sp² hybridization: 33.33% s-character
- sp³ hybridization: 25% s-character

2. **Analyze Each Compound**:
We need to look at the compounds given in the options and identify the hybridization of the carbon atom marked with an asterisk in each case.

3. **Determine Hybridization for Each Option**:
- **Option A**: The carbon marked with an asterisk forms 4 sigma bonds (no lone pairs), indicating sp³ hybridization.
- **Option B**: The carbon marked with an asterisk forms 3 sigma bonds and 1 pi bond (the pi bond does not count towards hybridization), indicating sp² hybridization.
- **Option C**: The carbon marked with an asterisk forms 2 sigma bonds and 2 pi bonds (only sigma bonds count), indicating sp hybridization.
- **Option D**: The carbon marked with an asterisk forms 3 sigma bonds and 1 pi bond, indicating sp² hybridization.

4. **Compare Electronegativity Based on Hybridization**:
- From the analysis:
- Option A (sp³) has the least electronegativity.
- Option B (sp²) has intermediate electronegativity.
- Option C (sp) has the highest electronegativity.
- Option D (sp²) also has intermediate electronegativity.

5. **Conclusion**:
The carbon marked with an asterisk in **Option C** is the most electronegative because it is sp hybridized, which has the highest s-character (50%).

### Final Answer:
The carbon marked with an asterisk is most electronegative in **Option C**.

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