Answer
The proton on the right is more acidic.
Work Step by Step
If we remove the left proton, the conjugate base will have these changes:
- The Hydrogen on the left will be removed.
- The Carbon that was connected to the Hydrogen will get a negative charge, because the electrons that were making the bond will turn into a lone pair.
If we remove the proton on the right, the conjugate base will have these changes:
- The Hydrogen on the right will be removed.
- The Oxygen that was connected to the hydrogen will get a negative charge, because the electrons that were making the bond will turn into a lone pair.
- But, since there is a pi bond next to the lone pairs of the oxygen, there will be a ressonance structure. Not only that one, but other structure will exist, with the other pi bond on the left.
- Therefore, the charge is spread between 3 carbons.
** You have to pay attention to the fact that, the carbon that was connected to the left proton, actually has a pi bond, which means that the pattern doesn't fit. But, the carbon that was connected to the right proton, has one bond between it and the pi bond, which means that our pattern works, because they are "next".
Since the charge on the second conjugate base will be more delocalized, it will be more stable.
If the second conjugate base is more stable, the proton on the right is more acidic.
