# Can terminal enols be reduced by using LiAlH4?

According to the solution given in my textbook, no reaction takes place in this case.

But I am not quite sure about it. I feel that the enol can easily tautomerize to aldehyde and we know that aldehydes are reduced by $\ce{LiAlH4}$ to give alcohols.

So, will the above reaction take place? What will be the final product after reduction occurs?

• What textbook? Is it worth posting a picture, so we can verify if the textbook is indeed incorrect (or perhaps there is some caveat)? – electronpusher Dec 23 '16 at 3:36

## 1 Answer

Not only can that enol easily tautomerize to the aldehyde, the aldehyde is the major component at equilibrium at room temperature (by a lot!). The equilibrium constant for the similar system of ethanal/vinyl alcohol (one carbon shorter than yours) is $K \approx 3\times 10^{-7}$ (source: Wikipedia page on keto-enol tautomerism):

$$\ce{ CH3CHO <=> CH2=CHOH}\\ K = \dfrac{[\ce{CH2=CHOH}]}{[\ce{CH3CHO}]}\approx 3\times 10^{-7}$$

Thus, for every molecule of enol in this system, there are $\sim 3 \times 10^6$ molecules of aldehyde. $\ce{LiAlH4}$ will reduce the aldehyde and then LeChâtelier's principle will drag the enol along for the ride.