Question

Ozonolysis of 2-methyl but-2-ene yields
(A) Only aldehyde
(B) Only ketone
(C) Both aldehyde and ketone
(D) None of these

Answer 1

Hint: In an organic reaction known as ozonolysis, ozone is used to break the unsaturated bonds in alkenes or alkynes. The carbonyl group has replaced the multiple carbon-carbon bonds. The type of multiple bonds being oxidised determines the products of the reaction.

Complete Step by Step Answer:
In the ozonolysis reaction, the ozone molecule is added to the double bond of 2-methyl but-2-ene. It forms ozonide. Alkenes can be easily converted to carbonyl compounds using ozone (${{O}_{3}}$) as it is a strong oxidant. In this reaction, both the sigma and pi bonds break. The ozonide formed undergoes hydrolysis in the presence of $Zn/{{H}_{2}}O$.

The products formed in this reaction are one mole of aldehyde and one mole of ketone. The aldehyde formed is acetaldehyde and ketone is acetone.
Correct Option: (C) Both aldehyde and ketone.

Additional Information: Ozone is thermodynamically unstable in comparison to oxygen because, when it breaks down into oxygen, heat is released ($\Delta H$ is negative) and entropy rises ($\Delta S$ is positive). Consequently, these two effects produce a significant negative Gibbs energy change ($\Delta G$) for the conversion of the ozone molecule into oxygen.

Note: Unsymmetrical alkenes produce two moles of different molecules, while symmetrical alkenes produce two moles of the same product molecule. As we know, ozone (${{O}_{3}}$) contains three oxygen atoms. Two of the oxygen atoms are used up in the reaction, forming the products. The third oxygen gets attached to $Zn$ forming $ZnO$.