The compound , which on reductive ozonolysis gives one mole of `O=CH-CH_2-CH_2-CH_2-CH=O`, is

Options

A. 1-methylbut -1-ene
B. 3-methylbut -1-ene
C. cyclopentane
D. 1,2- dimethylpropene

Answer

To solve the question, we need to determine the compound that, upon undergoing reductive ozonolysis, yields one mole of the compound \( O=CH-CH_2-CH_2-CH_2-CH=O \).

### Step-by-Step Solution:

1. **Identify the Product Structure**:
The product given is \( O=CH-CH_2-CH_2-CH_2-CH=O \). This can be rewritten as:
\[ CHO-CH_2-CH_2-CH_2-CHO \]
This indicates that the product contains two aldehyde groups at both ends of a five-carbon chain.

2. **Understanding Reductive Ozonolysis**:
Reductive ozonolysis involves the cleavage of double bonds in alkenes using ozone (O3), followed by reduction (commonly with zinc and water) to yield carbonyl compounds (aldehydes or ketones).

3. **Constructing the Precursor Compound**:
Since the product has two aldehyde groups, we can deduce that the precursor compound likely has a double bond between two carbon atoms, which will be cleaved during ozonolysis.

4. **Formulating the Alkene**:
To obtain the product \( CHO-CH_2-CH_2-CH_2-CHO \), we can visualize that the original compound must be an alkene that, when ozonolyzed, will yield two aldehyde groups. The simplest structure that fits this description is 1-pentene or cyclopentene.

5. **Testing Cyclopentene**:
Let's consider cyclopentene:
- The structure of cyclopentene is a five-membered ring with one double bond.
- When subjected to ozonolysis, the double bond will break, leading to the formation of two aldehyde groups at the ends of the chain.

6. **Confirming the Reaction**:
- The ozonolysis of cyclopentene would yield the product \( CHO-CH_2-CH_2-CH_2-CHO \), which matches our target product.
- Therefore, the compound that gives the desired product upon reductive ozonolysis is cyclopentene.

7. **Final Answer**:
The compound that, upon reductive ozonolysis, gives one mole of \( O=CH-CH_2-CH_2-CH_2-CH=O \) is **cyclopentene**.