How many structural isomers are possible for the molecular formula `C_(4)H_(8)` which can undergo ozonolysis ?

Options

A. 2
B. 4
C. 3
D. 1

Answer

To determine how many structural isomers are possible for the molecular formula \( C_4H_8 \) that can undergo ozonolysis, we can follow these steps:

### Step 1: Determine the Degree of Unsaturation
The degree of unsaturation can be calculated using the formula:
\[ \text{Degree of Unsaturation} = \frac{2C + 2 + N - H - X}{2} \]
For \( C_4H_8 \):
- \( C = 4 \)
- \( H = 8 \)
- \( N = 0 \) (no nitrogen)
- \( X = 0 \) (no halogens)

Substituting these values into the formula:
\[ \text{Degree of Unsaturation} = \frac{2(4) + 2 + 0 - 8 - 0}{2} = \frac{8 + 2 - 8}{2} = \frac{2}{2} = 1 \]
This indicates that there is one degree of unsaturation, which means there could be either a double bond (alkene) or a ring structure.

### Step 2: Identify Possible Structural Isomers
Since we are interested in structural isomers that can undergo ozonolysis, we will focus on alkenes (as cycloalkanes like cyclobutane and methylcyclopropane do not undergo ozonolysis).

The possible structural isomers of alkenes for \( C_4H_8 \) are:
1. **But-1-ene**: \( CH_2=CH-CH_2-CH_3 \)
2. **But-2-ene**: \( CH_3-CH=CH-CH_3 \) (this can exist as cis and trans isomers)
3. **Cyclobutane**: \( C_4H_8 \) (does not undergo ozonolysis)
4. **Methylcyclopropane**: \( C_4H_8 \) (does not undergo ozonolysis)

### Step 3: List the Alkenes that Can Undergo Ozonolysis
The relevant alkenes that can undergo ozonolysis are:
1. **But-1-ene**: Ozonolysis yields butanal.
2. **But-2-ene**: Ozonolysis yields two molecules of acetaldehyde (for both cis and trans).

### Step 4: Count the Isomers
From the above analysis, the structural isomers of \( C_4H_8 \) that can undergo ozonolysis are:
1. But-1-ene
2. But-2-ene (cis and trans)

Thus, there are a total of **three structural isomers** of \( C_4H_8 \) that can undergo ozonolysis.

### Final Answer
The number of structural isomers of \( C_4H_8 \) that can undergo ozonolysis is **3**.

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