IUPAC name of `CH_(3) - underset(CH_(3))underset(|)CH-CH_(2) - underset(CN)underset(|)CH-CH_(3)`

Explanation

To determine the IUPAC name of the compound `CH₃ - CH(CH₃) - CH - CH₂ - CN`, we will follow a systematic approach.

### Step-by-Step Solution:

1. **Identify the Longest Carbon Chain**:
- The longest continuous carbon chain in the compound is 5 carbons long. This is because we can trace a path through the carbon atoms without breaking the chain.
- The structure can be visualized as follows:
```
CH₃
|
CH - CH₂ - CH - CN
|
CH₃
```

2. **Number the Carbon Chain**:
- We will number the carbon chain starting from the end closest to the functional group (in this case, the nitrile group -CN).
- The numbering will be as follows:
```
1 2 3 4 5
CH₃ - CH - CH₂ - CH - CN
```

3. **Identify Substituents**:
- The substituents on the main chain are two methyl groups (CH₃) attached to the second and fourth carbon atoms.
- Therefore, we have:
- Methyl group at position 2
- Methyl group at position 4

4. **Combine the Information**:
- The base name for a 5-carbon chain is "pentane".
- Since we have two methyl groups, we denote this as "dimethyl".
- The positions of the methyl groups are 2 and 4, so we write this as "2,4-dimethyl".

5. **Include the Functional Group**:
- Since we have a nitrile (-CN) group, we add "nitrile" to the name.
- The nitrile group takes precedence in naming, so we write it as "pentanenitrile".

6. **Final IUPAC Name**:
- Combining all the parts, the final IUPAC name of the compound is **2,4-dimethylpentanenitrile**.

### Final Answer:
The IUPAC name of the compound is **2,4-dimethylpentanenitrile**.