How many different primary alkyl groups are possible with `C_(5)H_(11)`?

Options

A. 3
B. 7
C. 5
D. 4

Explanation

To determine how many different primary alkyl groups are possible with the molecular formula \( C_5H_{11} \), we will follow these steps:

### Step 1: Understand Primary Alkyl Groups
A primary alkyl group is defined as an alkyl group where the carbon atom that is attached to the rest of the molecule is a primary carbon. A primary carbon is one that is attached to only one other carbon atom.

### Step 2: Identify the Structure of \( C_5H_{11} \)
The molecular formula \( C_5H_{11} \) indicates that we have 5 carbon atoms and 11 hydrogen atoms. The general structure can be represented as a straight-chain or branched-chain alkane.

### Step 3: Draw the Main Chain
Start by drawing the main chain of 5 carbon atoms (pentane):
```
C - C - C - C - C
```
This structure represents n-pentane, which is a straight-chain alkane.

### Step 4: Create Different Primary Alkyl Groups
Now, we will create different primary alkyl groups by substituting one of the terminal carbons with a different group while ensuring that the carbon we are attaching to is still a primary carbon.

1. **n-Pentyl group**:
- Structure: \( CH_3(CH_2)_4CH_2- \) (5 carbons in a straight chain)

2. **Isopentyl group** (or 2-methylbutyl):
- Structure: \( CH_3CH(CH_3)(CH_2)CH_2- \) (4 carbons in a chain with a methyl group on the second carbon)

3. **Neopentyl group** (or 2,2-dimethylpropyl):
- Structure: \( (CH_3)_2C(CH_2)CH_2- \) (3 carbons in a chain with two methyl groups on the second carbon)

4. **Sec-butyl group** (or 1-methylbutyl):
- Structure: \( CH_3CH_2CH(CH_3)CH_2- \) (4 carbons in a chain with a methyl group on the third carbon)

### Step 5: Count the Different Primary Alkyl Groups
After analyzing the structures, we find that there are 4 different primary alkyl groups possible with the formula \( C_5H_{11} \):
1. n-Pentyl
2. Isopentyl
3. Neopentyl
4. Sec-butyl

### Conclusion
Thus, the total number of different primary alkyl groups possible with \( C_5H_{11} \) is **4**.

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