Reaction of enols with electrophiles

In a reaction between an enol and an electrophile which will attack the electrophile, the oxygen of the $\ce{-OH}$ group or the pi electrons of the the double bond?

This is my attempt at a solution: Since, the oxygen atom has two lone pair of electrons it should be more electron rich than the double bond and therefore it should attack the eletrophile, Am i correct?

• It depends and number of lone pairs doesn't matter. – Mithoron Feb 15 '16 at 13:12
• 1) How have you got a measurable concentration of enol in the first place? 2) think about stability of the resulting particle and 3) this actually strongly depends on the electrophile in question. Furthermore, often the attack and the whole reaction are reversible and it the product is defined not but preferable attack position but by thermodynamical stability of the alternative products. – permeakra Apr 15 '16 at 17:56

1 Answer

The functional group in question is a vinyl alcohol, and it is a mistake to consider these groups as isolated. The oxygen is in conjugation with the vinyl group, meaning that resonance favors the entire system attacking. There is no way to leverage conjugation as an energetic driving force if the oxygen attacks by itself.

This is almost the same as your other question:

Hydrolysis of 3,4-dihydropyran