Question

How can you reverse ozonolysis?

Answer 1

With some difficulty.........

Explanation:

With some difficulty in that when ozonolysis is performed, typically we BREAK `C=C` bonds......i.e.

`R_1R_2C=CR_3R_4stackrel(O_3)rarrR_2R_2C=O+O=CR_3R_4`

And for the reverse reaction we have to perform a `C-C` coupling reaction, a notoriously difficult proposition in organic chemistry.

And thus from an olefin (for instance) ozonolysis gives 2 ketones whose identity could be established by the classical means of chemical analysis: melting points of derivatives. There are quite probably some modern means of organic synthesis that could couple two ketones (the `"Mcmurry reaction"`, perhaps, which uses `TiCl_4` and `Zn`), anyway you can look this up in your organic text.