8-31 - Organic Chemistry (Mcmurry)

Question

Propose a curved-arrow mechanism to show how ozone (O₃) reacts

with a carbon–carbon double bond to form a molozonide, the first intermediate

in ozonolysis.

Step-by-Step Solution

Answer

Curved-arrow mechanism:

Ozonolysis

Christian Fredrich Schonbein was the one who did ozonolysis firstly further Carl Dietrich Harries attributed in the ozonolysis of alkene therefore; this reaction was also named as Harries ozonolysis. Ozonolysis is a type of oxidation reaction. With the help of ozone  (O₃) unsaturated hydrocarbons such as alkene or alkyne can be directly converted into aldehyde or ketone. 

Ozonolysis of alkene can be shown as:

                                   Ozonolysis of alkene

Molozonide

Molozonide is an unstable intermediate formed in the first step of ozonloysis. In the mechanism to form molozonide, 1 mole of ozone () will react with the alkene. It is a concerted (in which formation of bond and breaking of bond takes place simultaneously) cycloaddition reaction.

Curved-arrow mechanism

Curved -arrow mechanism to form molozonide with the help of ozone and alkene having carbon atoms is as shown below:

                                Formation of Molozonide