Theoretical study on enol-keto tautomerism of α-fluorine-β- diketones

Density Functional Theory method is applied to investigate the enol-keto tautomerism of both acyclic and cyclic α-fluorine-β-diketones. It is shown that, for acyclic cases, α-fluorine could improve the relative stability of keto tautomer by lessening intramolecular hydrogen bond of enol form, whereas the relative stability of cyclic enol could be attributed to two factors: destabilization of keto and stabilization of enol. Furthermore, the relative stabilities of all enol tautomers are improved in THF to different extents.