tautomer - Compound having the highest enol content will be?

The answer written in book is 3 but no solution is given.After referring to some other question I think that hydrogen bonding can take place in compounds like 3 but am not sure about it. Am I right that it is the only reason why it has the highest enol content?I would like to ask one more thing that, while comparing the keto and enol content, if in a compound more than one ketone is present, than do we enolize any one of them only to check?...Read more

Enol content tautomers

I have figured out that 4 one will have the highest enol content of all, and the 1 structure would come after 4 in enol content, i.e 4 > 1. Then I got confused between the 2nd and the 3rd structures.Please give a brief explanation for the answer as well....Read more