Major form of methyl 3-hydroxy pent-2-enoate? I came across this question in a test:


  The enol form is the ________ form for 3-hydroxy pent-2-enoate?  (major/minor)


My argument is that the enol form must be more stable because of hydrogen bonding in the enol form and subsequent six membered ring formation (chelation). However the keto form has no such stabilization factor. Hence according to me the enol form must be more stable. But sadly, that is the wrong answer. What's going wrong?

Structure for reference:
quick googling shows that for a very similar compound ethyl acetoacetate enol and ketoforms are in equilibrium with 10% of enol form. However, this equilibrium is influenced by solvent significantly. Actually, the percentage shows that the difference in stability between these two forms is veeery little. 

The difference may be attributed to the difference in stability of the bonds, i.e.   C=O + C-H is better then C=C + C-O + O-H. However, internal hydrogen bonding DOES exist and participates in stability of enol form. For example, for hexan-1,3-one, the percentage of enol form is much lower.