Among the following the one having longest chain is

Options

A. neo-pentane
B. iso-pentane
C. 2-methylpentane
D. 2,2-dimethylbutane

Explanation

To determine which compound has the longest carbon chain among the given options, we will analyze each compound step by step.

### Step 1: Identify the Compounds
We have the following compounds to consider:
1. Neopentane
2. Isopentane
3. 2,2-Dimethylbutane
4. 2-Methylpentane

### Step 2: Draw the Structures
Let's draw the structures of each compound to visualize the carbon chains.

1. **Neopentane (C5H12)**:
- Structure:
```
CH3
|
CH3- C - CH3
|
CH3
```
- Parent chain: 3 carbon atoms (C-C-C)

2. **Isopentane (C5H12)**:
- Structure:
```
CH3
|
CH3- C - CH2 - CH3
|
CH3
```
- Parent chain: 5 carbon atoms (C-C-C-C-C)

3. **2,2-Dimethylbutane (C6H14)**:
- Structure:
```
CH3
|
CH3- C - CH2 - CH3
|
CH3
```
- Parent chain: 4 carbon atoms (C-C-C-C)

4. **2-Methylpentane (C6H14)**:
- Structure:
```
CH3
|
CH3- C - CH2 - CH3
|
CH2 - CH3
```
- Parent chain: 5 carbon atoms (C-C-C-C-C)

### Step 3: Count the Carbon Atoms in the Parent Chain
Now, let's count the number of carbon atoms in the longest continuous chain for each compound:
- Neopentane: 3 carbon atoms
- Isopentane: 5 carbon atoms
- 2,2-Dimethylbutane: 4 carbon atoms
- 2-Methylpentane: 5 carbon atoms

### Step 4: Determine the Longest Chain
From the counts above, we can see:
- Neopentane has 3 carbon atoms.
- Isopentane has 5 carbon atoms.
- 2,2-Dimethylbutane has 4 carbon atoms.
- 2-Methylpentane has 5 carbon atoms.

The compounds with the longest chains are Isopentane and 2-Methylpentane, both having 5 carbon atoms in their longest chain.

### Conclusion
Among the given options, **Isopentane and 2-Methylpentane** have the longest chains, each with 5 carbon atoms.