Tautomer equilibrium given in Fig. 1 shows that two keto-enol tautomerisms are possible for β-dicarbonyls. The position of the keto-enol equilibrium for this class of compounds differs according to electronic characteristics of the substitutions and the nature of the solvents. The cis-enol forms of β-dicarbonyls are stabilized by a strong intramolecular hydrogen bond [1-3]. Several experimental data suggest that electron-withdrawing group substitution at β-position, such as the trifluoromethyl group (−CF3), decreases the strength of the intramolecular hydrogen bond (IHB), whilst substitution of alkyl group in this position increases the IHB strength. 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, TFMHD, has two different β- substituted groups with different electron-withdrawing, donating and steric effects. Therefore, it is interesting to cross-check these effects on conformational stabilities, molecular structure and IHB strength. The aim of the present paper is to predict IHB strength of TFMHD by means of density functional theory (DFT) levels.

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