Ozonolysis is a reaction in which an alkene reacts with ozone (O3) to form an ozonide intermediate, which then decomposes to form carbonyles. The reaction involves the addition of ozone across the double bond of the alkene, resulting in the cleavage of the carbon-carbon double bond. For symmetrical alkenes, two identical carbonyl compounds are formed, while for asymmetrical alkenes, a mixture of different carbonyl compounds is obtained.