How many isomers are possible for the alkyl group `C_(4)H_(9)-`?

Options

A. Two
B. Three
C. Four
D. Five

Answer

To determine how many isomers are possible for the alkyl group \( C_4H_9^- \), we can follow these steps:

### Step 1: Understand the Structure
The alkyl group \( C_4H_9^- \) is derived from the alkane \( C_4H_{10} \) (butane) by removing one hydrogen atom. This means we are looking for different structural arrangements of four carbon atoms with nine hydrogen atoms.

### Step 2: Identify the Possible Carbon Skeletons
We can start by drawing the possible carbon skeletons (the arrangement of carbon atoms):

1. **Straight-chain (n-butyl)**:
- Structure: \( CH_3-CH_2-CH_2-CH_2- \)

2. **Branched-chain isomers**:
- **Isobutyl**:
- Structure: \( (CH_3)_2CH-CH_2- \)
- **Sec-butyl**:
- Structure: \( CH_3-CH(CH_3)-CH_2- \)
- **Tert-butyl**:
- Structure: \( (CH_3)_3C- \)

### Step 3: Count the Isomers
Now, we can count the distinct structural isomers we have identified:
1. n-butyl
2. Isobutyl
3. Sec-butyl
4. Tert-butyl

### Conclusion
Thus, there are a total of **4 isomers** possible for the alkyl group \( C_4H_9^- \).