Step 1: Understanding the Concept:
To determine the IUPAC name of an alkane, we must identify the longest continuous carbon chain (the parent chain) and then number the carbon atoms to give the lowest possible locant (number) to any substituent groups.
Step 2: Detailed Explanation:
Let's analyze the given structure: $\text{CH}_3 - \text{CH}_2 - \text{CH}(\text{CH}_3) - \text{CH}_2 - \text{CH}_3$.
1. Identify the longest carbon chain: The longest straight chain contains 5 carbon atoms. Therefore, the parent alkane is "pentane".
2. Identify the substituents: There is a methyl group ($-\text{CH}_3$) attached to the main chain.
3. Number the carbon chain: We number the chain from left to right or right to left to give the substituent the lowest possible number.
- Numbering left to right: $\text{C}_1(\text{CH}_3) - \text{C}_2(\text{CH}_2) - \text{C}_3(\text{CH}(\text{CH}_3)) - \text{C}_4(\text{CH}_2) - \text{C}_5(\text{CH}_3)$. The methyl group is at carbon-3.
- Numbering right to left: It also places the methyl group at carbon-3.
Since the position is 3 from either direction, the substituent is firmly at the 3rd carbon.
Combining these parts, the IUPAC name is 3-Methylpentane.
Step 3: Final Answer:
The IUPAC name of the compound is 3-Methylpentane. The correct option is (A).