Which of the following compounds will exhibit cis-trans (geometrical) isomerism?

Options

A. But-2-ene
B. But-2-yne
C. Butan-2-ol
D. But-1-ene

Answer

To determine which of the given compounds will exhibit cis-trans (geometrical) isomerism, we need to analyze the structures of the compounds and check if they meet the necessary conditions for geometrical isomerism.

### Step-by-Step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism, also known as cis-trans isomerism, occurs in alkenes where there is restricted rotation around a double bond.
- For a compound to exhibit cis-trans isomerism, it must have two different groups attached to each carbon of the double bond.

2. **Identifying the Compounds**:
- Let's analyze the provided options. We will focus on alkenes since only they can exhibit cis-trans isomerism.

3. **Analyzing But-2-ene**:
- Structure: CH3-CH=CH-CH3
- In but-2-ene, the double bond is between the second and third carbon atoms.
- Groups attached to the double bond are:
- C2: CH3 (R1) and H (R2)
- C3: H (R3) and CH3 (R4)
- Since R1 (CH3) is not equal to R2 (H) and R3 (H) is not equal to R4 (CH3), but-2-ene can exhibit cis-trans isomerism.

4. **Analyzing Butane**:
- Butane is a straight-chain alkane (C4H10) and does not have a double bond.
- Since it is not an alkene, butane cannot exhibit geometrical isomerism.

5. **Analyzing Bute-1-ene**:
- Structure: CH2=CH-CH2-CH3
- In bute-1-ene, the double bond is between the first and second carbon atoms.
- Groups attached to the double bond are:
- C1: H (R1) and CH2 (R2)
- C2: CH2 (R3) and CH3 (R4)
- Here, R1 (H) is equal to R2 (H), which means bute-1-ene cannot exhibit geometrical isomerism.

6. **Conclusion**:
- The only compound that exhibits cis-trans isomerism among the options is but-2-ene.

### Final Answer:
The compound that will exhibit cis-trans (geometrical) isomerism is **but-2-ene**.