An olefin was treated with ozone and the resulting ozonide on hydrolysis gave 2-pentanone and acetaldehyde. Write equations for the reaction involved.

Answer

To solve the problem, we need to identify the olefin that, when treated with ozone (O3), yields 2-pentanone and acetaldehyde upon hydrolysis. Let's break down the steps to arrive at the solution.

### Step 1: Identify the Products
The products given are:
- 2-pentanone (C5H10O)
- Acetaldehyde (C2H4O)

### Step 2: Determine the Structure of 2-Pentanone and Acetaldehyde
- **2-Pentanone** has the structure:
\[ CH3-CH2-CO-CH2-CH3 \]
- **Acetaldehyde** has the structure:
\[ CH3CHO \]

### Step 3: Determine the Number of Carbons
Counting the total number of carbons in the products:
- 2-pentanone has 5 carbons.
- Acetaldehyde has 2 carbons.
- Total = 5 + 2 = 7 carbons.

### Step 4: Identify the Olefin
To produce these products via ozonolysis, we need an olefin (alkene) that has 7 carbons. The structure that fits this requirement is **3-methyl-hex-2-ene**:
\[ CH3-CH2-CH(CH3)-CH=CH-CH3 \]

### Step 5: Write the Ozonolysis Reaction
The ozonolysis of 3-methyl-hex-2-ene can be represented as follows:
1. The alkene reacts with ozone (O3) to form an ozonide.
2. The ozonide is then hydrolyzed (usually with Zn and water) to yield the carbonyl compounds.

The reaction can be summarized as:
\[ \text{3-methyl-hex-2-ene} + O3 \rightarrow \text{ozonide} \]
\[ \text{ozonide} + H2O \xrightarrow{Zn} 2-pentanone + acetaldehyde \]

### Step 6: Write the Final Equations
1. **Formation of Ozonide**:
\[ CH3-CH2-CH(CH3)-CH=CH-CH3 + O3 \rightarrow \text{ozonide} \]
2. **Hydrolysis of Ozonide**:
\[ \text{ozonide} + H2O \xrightarrow{Zn} CH3-CH2-CO-CH2-CH3 + CH3CHO \]

### Final Answer
The complete reaction can be summarized as:
\[ CH3-CH2-CH(CH3)-CH=CH-CH3 + O3 \rightarrow \text{ozonide} \rightarrow CH3-CH2-CO-CH2-CH3 + CH3CHO \]