Question

What is the name of the hydrocarbon that yields ethanal and propanone upon reductive ozonolysis?

• A. But-2-ene
• B. 2-Methylbut-2-ene
• C. 2-Methylbut-1-ene
• D. Pent-2-ene

Hint:

In ozonolysis problems, determine the alkene by combining the carbon fragments of the aldehydes or ketones formed after cleavage of the double bond.

Answer 1

The Correct Option is B

Topic - Organic Chemistry: Hydrocarbons (Alkenes)
Step 1: Understanding the Question:
We need to find an alkene that, when reacted with ozone followed by Zn/H\(_2\)O, breaks into Ethanal and Propanone.
Step 2: Key Formula or Approach:
In ozonolysis, the \(C=C\) bond is cleaved. To find the original alkene, remove the oxygen atoms from the products and join the carbons with a double bond.
Step 3: Detailed Solution:
Products given:
1. Ethanal: \(CH_3-CHO\)

2. Propanone: \(CH_3-CO-CH_3\)
Write them facing each other at the carbonyl groups:
\[ CH_3-CH=O \quad + \quad O=C(CH_3)_2 \]
Remove the oxygens and join the carbons:
\[ CH_3-CH=C(CH_3)_2 \]
Naming the product:
The longest chain has 4 carbons (But-ene).
There is a methyl group at position
2.
The double bond starts at position
2.
Name: 2-Methylbut-2-ene.
Step 4: Final Answer:
The hydrocarbon is 2-Methylbut-2-ene.