Which of the following represents 3-methylpenta-1,3-diene?

Options

A. `CH_(2)=CH(CH_(2))_(2)CH_(3)`
B. `CH_(2)=CHCH(CH_(3))CH_(2)CH_(3)`
C. `CH_(3)CH=C(CH_(3))CH=CH_(2)`
D. `CH_(3)CH=C(CH_(3))_(2)`

Answer

To determine which structure represents 3-methylpenta-1,3-diene, we need to follow these steps:

### Step-by-Step Solution:

1. **Understand the Name**: The compound is named 3-methylpenta-1,3-diene. This indicates:
- "penta" means there are 5 carbon atoms in the longest chain.
- "1,3-diene" indicates there are double bonds at the first and third positions of the carbon chain.
- "3-methyl" indicates there is a methyl group (–CH₃) attached to the third carbon of the chain.

2. **Draw the Carbon Chain**: Start by drawing a straight chain of 5 carbon atoms (C1, C2, C3, C4, C5).

```
C1 - C2 - C3 - C4 - C5
```

3. **Add the Double Bonds**: Place double bonds at the first and third positions:
- Between C1 and C2
- Between C3 and C4

```
C1=C2 - C3=C4 - C5
```

4. **Add the Methyl Group**: Attach a methyl group (–CH₃) to the third carbon (C3):
- This means C3 will have one hydrogen replaced by a methyl group.

```
C1=C2 - C3(CH₃) = C4 - C5
```

5. **Final Structure**: The final structure should look like this:

```
CH2=C(CH3)-C=C-CH3
```

6. **Verify the Structure**: Count the total number of carbons and check the positions of the double bonds and the methyl group:
- Total Carbons: 5 (C1, C2, C3, C4, C5)
- Double Bonds: Present at C1 and C3
- Methyl Group: Present at C3

### Conclusion:
The correct representation of 3-methylpenta-1,3-diene is the structure we derived above.