Chapter 11, Problem 59DSP

Interpretation Introduction

Interpretation:

The structure for compound X is to be determined in the given fragmentation-recombination process of alkenes.

Concept introduction:

$\text{1,3-dipoles}$

are represented by a Lewis structure such that four electrons $\text{(4π)}$

are delocalized over three atoms. One of them is positively charged while the other is negatively charged. The positively charged carbon atom remains unchanged.

The alkene is the $\text{2π}$

electron component.

This dipole acts as a $\text{4π}$ electron component and can add to an alkene with $\text{2π}$

electron component via the $\text{[4+2]-cycloaddition}$.

The second step in the mechanism of ozonolysis of alkenes undergoes a fragmentation-recombination process.

The fragmentation step is the reverse of a $\text{1,3-dipolar}$

cycloaddition step.

The fragmentation of ozonide yields a carbonyl compound and a $\text{1,3-dipolar}$

compound.

The carbonyl compound and $\text{1,3-dipolar}$

compound react again to give a product via $\text{1,3-dipolar}$

cycloaddition.

For an unsymmetrical $\text{2π}$

electron component, the two ends of the double bond constitute two possible sites of reaction.

In the fragmentation process, the single bond between two carbon atoms attached to the oxygen atoms in the ozonide breaks.