When a stream of ozonised oxygen is passed through a solution of an alkene, in organic solvent, an unstable addition cyclocompound, ozonide is formed which on reduction with zinc dust and water forms an aldehyde or a ketone or a mixture of both.
1. Formaldehyde :
Under these conditions ethylene gives formaldehyde.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=900933491554497832)
2. Acetaldehyde :
Symmetrically disubstituted alkene like but-2-ene gives acetaldehyde.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=9567701492429731238)
3. Acetone :
Tetrasubshtwed alkene like 2,3-dimethyl but-2-ene gives acetone.
![](https://www.sarthaks.com/?qa=blob&qa_blobid=14096929358246774115)