How many n-octene can show geometrical isomerism?

Answer

To determine how many n-octenes can show geometrical isomerism, we need to analyze the structures of n-octene and identify the presence of double bonds and substituents around those double bonds.

### Step-by-Step Solution:

1. **Understanding Geometrical Isomerism**:
- Geometrical isomerism occurs in alkenes (compounds with a carbon-carbon double bond) when there are different groups attached to the carbon atoms involved in the double bond.
- For geometrical isomerism to occur, the two groups attached to each carbon of the double bond must be different. This means that if we have a structure like C=C with groups R1, R2 on one carbon and R3, R4 on the other, R1 must not equal R2 and R3 must not equal R4.

2. **Identifying the Structure of n-Octene**:
- n-Octene has the formula C8H16 and can be represented as CH3(CH2)5CH=CH2.
- It can exist in several structural forms (isomers) depending on the position of the double bond.

3. **Analyzing Different Isomers**:
- The possible positions for the double bond in n-octene are between the following carbon atoms:
- Between C1 and C2
- Between C2 and C3
- Between C3 and C4
- Between C4 and C5
- Between C5 and C6
- Between C6 and C7
- We will analyze each of these positions to see if they can exhibit geometrical isomerism.

4. **Position of the Double Bond**:
- **1-Octene (C1=C2)**: This cannot show geometrical isomerism because both groups on C1 are hydrogen.
- **2-Octene (C2=C3)**: This can show geometrical isomerism since C2 has CH3 and H, and C3 has H and CH2(CH2)3CH3. This gives rise to cis (same side) and trans (opposite side) isomers.
- **3-Octene (C3=C4)**: Similar to 2-octene, this can also show geometrical isomerism with different groups on C3 and C4.
- **4-Octene (C4=C5)**: This can show geometrical isomerism as well.
- **5-Octene (C5=C6)**: This can also show geometrical isomerism.
- **6-Octene (C6=C7)**: This cannot show geometrical isomerism because both groups on C6 are hydrogen.

5. **Counting the Isomers**:
- From the analysis:
- 1-Octene: 0 isomers
- 2-Octene: 2 isomers (cis and trans)
- 3-Octene: 2 isomers (cis and trans)
- 4-Octene: 2 isomers (cis and trans)
- 5-Octene: 2 isomers (cis and trans)
- 6-Octene: 0 isomers
- Total geometrical isomers = 0 + 2 + 2 + 2 + 2 + 0 = 8.

### Final Answer:
Thus, the total number of n-octenes that can show geometrical isomerism is **8**.