Carbon-carbon double bond lenghth will be maximum in which of the following compounds ?

Options

A. `CH_(3)-CH=CH_(2)`
B. `CH_(3)-CH=CH-CH_(3)`
C. `CH_(3)-underset(CH_(3))underset(|)C=underset(CH_(3))underset(|)C-CH_(3)`
D. `CH_(2)=CH_(2)`

Explanation

To determine which compound has the maximum carbon-carbon double bond length, we need to analyze the compounds based on their hyperconjugation and the number of alpha hydrogens present.

### Step-by-Step Solution:

1. **Understanding Carbon-Carbon Double Bonds**:
- Carbon-carbon double bonds (C=C) can vary in length depending on the bond order and the presence of hyperconjugation. The higher the bond order, the shorter the bond length. Conversely, if the bond has more single bond character, the bond length will be longer.

2. **Identifying Hyperconjugation**:
- Hyperconjugation involves the delocalization of sigma electrons from adjacent C-H bonds to the π bond of the double bond. This effect can stabilize the double bond and reduce its character, leading to a longer bond length.

3. **Counting Alpha Hydrogens**:
- Alpha hydrogens are the hydrogens attached to the carbon atom adjacent to the carbon-carbon double bond. The more alpha hydrogens present, the greater the hyperconjugation effect, which results in a longer C=C bond.

4. **Analyzing the Given Compounds**:
- Let's consider the compounds one by one:
- **Compound 1**: CH3-CH=CH2 (3 alpha hydrogens)
- **Compound 2**: CH3-CH(CH3)-CH=CH2 (6 alpha hydrogens)
- **Compound 3**: CH3-CH(CH3)-CH(CH3)-CH=CH2 (12 alpha hydrogens)
- **Compound 4**: CH2=CH2 (no alpha hydrogens)

5. **Comparing Hyperconjugation**:
- Compound 1 has 3 alpha hydrogens, which allows for some hyperconjugation.
- Compound 2 has 6 alpha hydrogens, leading to more hyperconjugation and thus a shorter double bond.
- Compound 3 has 12 alpha hydrogens, resulting in the most hyperconjugation and the longest C=C bond.
- Compound 4 has no alpha hydrogens, meaning it has the highest double bond character and thus the shortest bond length.

6. **Conclusion**:
- Based on the analysis, Compound 3 (with 12 alpha hydrogens) will have the maximum carbon-carbon double bond length due to the highest degree of hyperconjugation.

### Final Answer:
The carbon-carbon double bond length will be maximum in Compound 3.