Which is maximum stable ?

Options

A. But-1-ene
B. cis-but-2-ene
C. trans-but-2-ene
D. All have equal

Answer

To determine which compound is the most stable among the given options, we will analyze them based on resonance, hyperconjugation, and inductive effects.

### Step-by-step Solution:

1. **Identify the Compounds**: We have three compounds to analyze: But-1-ene, Cis-but-2-ene, and Trans-but-2-ene.

2. **Check for Resonance**:
- Resonance involves the delocalization of electrons across adjacent pi bonds or lone pairs.
- In this case, all three compounds have only one double bond, which means resonance is not significant for any of them.

3. **Analyze Hyperconjugation**:
- Hyperconjugation refers to the interaction of the electrons in a sigma bond (usually C-H or C-C) with an adjacent pi bond or empty p-orbital.
- The stability provided by hyperconjugation increases with the number of alpha hydrogens (hydrogens attached to the carbon adjacent to the double bond).

4. **Count Alpha Hydrogens**:
- **But-1-ene**:
- Structure: CH2=CH-CH2-CH3
- Alpha Hydrogens: 2 (from the CH2 group next to the double bond).
- **Cis-but-2-ene**:
- Structure: CH3-CH=CH-CH3 (cis configuration).
- Alpha Hydrogens: 6 (3 from each CH3 group).
- **Trans-but-2-ene**:
- Structure: CH3-CH=CH-CH3 (trans configuration).
- Alpha Hydrogens: 6 (3 from each CH3 group).

5. **Compare Stability**:
- Since resonance is not a factor, we focus on hyperconjugation.
- But-1-ene has 2 alpha hydrogens, while both cis-but-2-ene and trans-but-2-ene have 6 alpha hydrogens each.
- More alpha hydrogens lead to greater hyperconjugation and thus greater stability.

6. **Conclusion**:
- Both cis-but-2-ene and trans-but-2-ene are more stable than but-1-ene due to higher hyperconjugation.
- Between cis and trans, trans-but-2-ene is generally more stable due to less steric strain (the bulky groups are on opposite sides).

### Final Answer:
**Trans-but-2-ene is the most stable compound among the three.**