[Sophia7X]

Solution:


This is the mechanism I first came up with:


I am wondering why it is incorrect. Why do you have to protonate the oxygen first, as opposed to starting off with a resonance structure?

Thanks.

[orgopete]

I could foresee two different mechanisms given the stated conditions. One possibility would be an intramolecular transfer of the proton. A similar step occurs in the decarboxylation of beta-ketoacids.

The other would involve a diprotio intermediate, as drawn in the "solution" and proposed solution. I find the proposed solution virtually identical to the "solution". The difference being whether one might draw a resonance structure of the starting material to increase the electron density of the carbonyl oxygen. I am not troubled by this. The "solution" holds more rigorously to electrons not moving in a concerted fashion. This may be more consistent with the notion of physics that someone like Einstein might favor, but chemists commonly favor concerted electron movements.