Hydrogen bond, for the first time, was suggested by Huggins in 1919 [1]. After this, large number of theoretical and experimental studies have been conducted to investigate the properties of intramolecular and intermolecular hydrogen bonding [2-3]. In an intramolecular hydrogen bond -IHB- system, both proton donor and proton acceptor groups, which may be of various kinds of functional groups, are located in the same molecule. The cis-enol forms of β-diketone, β-aminoenone, and β-enaminoimine molecules are engaged in such a hydrogen bond system and could be stabilized by a six membered-chelated ring [4]. The aim of this study is Intramolecular hydrogen bonding -IHB- of a series of molecules, as the simplest resonance-assisted hydrogen bond system in symmetric O–H…O class, have been studied at the DFT-B3LYP/6-311++G-d,p- level of theory. Good linear regressions between IHB energies based on Espinosa’s equation [5] with total electronic density, Laplacian of total electronic density in critical points, geometrical bond lengths, bond angels and NMR chemical shifts of bridged hydrogen were obtained.

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