# Why is the ketone more stable than its tautomer enol?

Jul 8, 2017

Well, sometimes it's not..........but enol formation in $\text{1,3-diketones}$ and $\text{1,3-diesters}$ is facilitated by the formation of a stable, heterocylic six-membered ring that is stabilized by hydrogen bonding.........

#### Explanation:

You know that ketones, and aldehydes, undergo some degree of $\text{keto-enol tautomerism}$:

$R C {H}_{2} C \left(= O\right) C {H}_{2} R r i g h t \le f t h a r p \infty n s R C H = C \left(- O H\right) C {H}_{2} R$

Sometimes, this equilibrium can be driven towards the RHS, the enol side by treating the starting material with a strong base to form the $\text{enolate}$.

In general for $\text{1,3-dicarboxylic acid derivatives}$, the equilibrium lies substantially to the right........

$\text{RO(O=)CCH"_2"C(=O)OR"rightleftharpoons"RO(O=)CCH=C("-"OH")"OR}$

This so-called $\text{enol}$ $\text{RO(O=)CCH=C("-"OH")"OR}$ contains an acidic hydrogen, and upon deprotonation this forms the basis for many $C - C$ bond formation reactions as a so-called $\text{carbanion}$. In your organic text there will be a whole chapter on $\text{carbanions and enolates}$.

And in the diagram enol formation is facilitated by the formation of a stable, heterocylic six-membered ring that is stabilized by hydrogen bonding.........