[TheArmchairSkeptic]

So I've been given a compound and am asked to rank the protons in order of acidity from most acidic to least acidic. I've drawn up the conjugate bases as shown here:

https://imgur.com/a/zGVsDPZ

Based on this, it seems to me that the order of acidity should be 3>1>2. I came to this conclusion using the ARIO rule; 3 and 1 should be more acidic than 2 because they have the negative charge on an oxygen while 2 has it on a carbon, and 3 is more acidic than 1 because it has a resonance structure that allows the negative charge to be shared between two oxygen atoms. Apparently though, the correct answer is 3>2>1, and I'm not sure why that is. I realize 2 has the resonance structure that allows the negative charge to be kicked up to the oxygen, but shouldn't the A rule supersede the R rule and make 1 more acidic than 2? I was told to use the rules in sequential order, so how come resonance seems to be more important than atom in this case?

Thanks in advance for any help.

[pgk]

In theory, the correct answer is 3 > 2 > 1 because the carbonyl group can form an enol which is more acidic than an alcohol and therefore, the α-methylene proton is more acidic than that of the alcohol.
But in practice, the correct answer is 3 > 1 > 2 because the so formed enol contains an additional (primary) vinyl alcohol group which is more acidic than a typical enol (or else, the A rule supersedes the R rule).
PS: If your teacher insists, the correct answer is 3 > 2 > 1 without any further comments.