[Spongebob]

Hello, dear chemists!

I am trying to draw a reaction mechanism and I am a little bit lost.
I upload the exersize and my ideas. Do you have any suggestions, what could happen next? Is this the right direction?

Thank you!

When we heat the first molecule in acetone/water (80/20), it converts to the following product.
I have to determine the mechanism, by which the reaction takes place.
It is related to the nucleophilic substitution reaction, and either hydride shift or shift of an alkyl group can occur.

[Babcock_Hall]

Which has a lower pK_a, water or acetone?  My hunch is that your proposal is more complex than it needs to be.

[MDG]

Might be as simple as protonation of oxirane oxygen atom followed by ring opening, cation rearrangement and ring closure to oxetane.

[Spongebob]

Wow, that is really simple and beautiful!... It have never occurred to me that the reaction can be internal.
Thanks a lot! Have a nice day

[Spongebob]

Might be as simple as protonation of oxirane oxygen atom followed by ring opening, cation rearrangement and ring closure to oxetane.

Wow, that is really simple and beautiful!... It have never occurred to me that the reaction can be internal.
Thanks a lot! Have a nice day

[pgk]

The proposed mechanism suffers of two weak points:
1). Water is not so strong acid that can protonate the oxirane ring.
2). Electron transfer from a single bond to the oxygen atom is not favorable.
However, oxirane can be hydrolyzed to the corresponding glycol in neutral conditions, though not easily.
So, try to write the same or a similar mechanism with the corresponding glycol (1,2-diol) or involving the preliminary hydrolysis of the ester group that is more easily hydrolyzed under neutral conditions and see which one fits better.
PS: Are you sure that there is not anything else present, e.g. a tertiary amine, an acid or a mineral salt?