The number of structure isomers possible from the molecular formula `C_(3)H_(9)N` is:

Options

A. 2
B. 3
C. 4
D. 5

Explanation

To determine the number of structural isomers for the molecular formula C3H9N, we will follow these steps:

### Step 1: Understand the molecular formula
The molecular formula C3H9N indicates that the compound contains 3 carbon (C) atoms, 9 hydrogen (H) atoms, and 1 nitrogen (N) atom.

### Step 2: Identify possible structures
We need to consider different ways to arrange the carbon atoms and the nitrogen atom, while ensuring that the total number of hydrogen atoms remains 9.

### Step 3: Draw structural isomers
1. **Propylamine (1-aminopropane)**:
- Structure: CH3-CH2-CH2-NH2
- This is a straight-chain primary amine.

2. **Isopropylamine (2-aminopropane)**:
- Structure: CH3-CH(NH2)-CH3
- This is another primary amine where the nitrogen is attached to the second carbon.

3. **N-Methyl-ethylamine**:
- Structure: CH3-NH-CH2-CH3
- This is a secondary amine where one of the carbon chains is a methyl group.

4. **N,N-Dimethylamine**:
- Structure: (CH3)2N-CH3
- This is a tertiary amine where the nitrogen is bonded to two methyl groups and one carbon chain.

### Step 4: Count the isomers
After drawing the above structures, we find that there are a total of **4 distinct structural isomers** for the molecular formula C3H9N.

### Final Answer
The number of structural isomers possible from the molecular formula C3H9N is **4**.

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