# What are tautomers? What applications do they have in modern chemistry?

Apr 10, 2016

Tautomers are constitutional isomers, that readily interconvert. The classic tautomerism is keto-enol tautomerism, which I will illustrate.

#### Explanation:

A ketone, for instance, acetone, has a enol tautomer:

${H}_{3} C - C \left(= O\right) C {H}_{3} r i g h t \le f t h a r p \infty n s {H}_{2} C = C \left(- O H\right) C {H}_{3}$

These are clearly constitutional isomers as they each have the same ${C}_{3} {H}_{6} O$ formula, but the equilibrium strongly lies to the left. With other diketones, for instance acetylacetone, the equilibrium lies more to the right.

As to the applications, such enol tautomerism allows for $C - C$ bond formation, as the enol hydrogen is acidic, and can be deprotonated to give ${H}_{2} C = C \left(- {O}^{-}\right) C {H}_{3}$, the enolate. The negative charge can be delocalized onto the carbon centre (i.e. as ${H}_{2}^{-} C - C \left(= O\right) C {H}_{3}$), the carbanion, and $C - C$ bond formation can be accomplished.