Chapter 24, Problem 24.60P

Interpretation Introduction

Interpretation:

Why ozone cracking of rubber occurs is to be explained.

Concept introduction:

Alkenes react with ozone in a reaction called ozonolysis. The $\text{C=C}$ bond of the alkene is broken and the two carbons are oxidized to carbonyl groups. The reaction starts with a $\text{[4 + 2]}$ cycloaddition of ozone across the $\text{π}$ bond to form a cyclic compound called molozonide that contains a $-\text{O}-\text{O}-\text{O}-$ bridge between the two carbons. This is followed by a rearrangement via a $\text{[4 + 2]}$ cyclo elimination and $\text{[4 + 2]}$ cycloaddition to an ozonide. In the ozonide, the carbons of the initial double bond are doubly bridged, by $-\text{O}-\text{O}-$ and $-\text{O}-$. The final reduction step converts the unstable ozonide to two carbonyl groups.