How many geometrical isomers are possible for the given compound?
`CH_(3)-CH=CH-CH=CH-C_(2)H_(5)`

Options

A. Four
B. Three
C. Two
D. Five

Answer

To determine the number of geometrical isomers for the compound `CH3-CH=CH-CH=CH-C2H5`, we can follow these steps:

### Step 1: Identify the Double Bonds
The given compound has two double bonds (C=C) between the carbon atoms. The presence of double bonds introduces the possibility of geometrical isomerism due to restricted rotation around these bonds.

### Step 2: Count the Restricted Rotations
Each double bond can lead to two configurations: cis (same side) and trans (opposite sides). In this compound, we have two double bonds, which means we have two points of restricted rotation.

### Step 3: Use the Formula for Geometrical Isomers
The number of geometrical isomers can be calculated using the formula:
\[ \text{Number of geometrical isomers} = 2^n \]
where \( n \) is the number of double bonds that can exhibit geometrical isomerism.

In our case, \( n = 2 \) (since there are two double bonds).

### Step 4: Calculate the Number of Isomers
Substituting \( n \) into the formula:
\[ \text{Number of geometrical isomers} = 2^2 = 4 \]

### Step 5: Identify the Isomers
We can identify the four geometrical isomers based on the configurations of the double bonds:
1. **Cis-Cis**: Both double bonds in the cis configuration.
2. **Cis-Trans**: The first double bond in cis and the second in trans.
3. **Trans-Cis**: The first double bond in trans and the second in cis.
4. **Trans-Trans**: Both double bonds in the trans configuration.

### Conclusion
Thus, the total number of geometrical isomers for the compound `CH3-CH=CH-CH=CH-C2H5` is **4**.

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