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Density functional theory method and B3LYP/6‐311++G(d,p) level of theory were used to determine the acidity of α‐carbon in the hydroxyl derivatives of beta diketones in the gas phase. An investigation of acidity strength in the gas phase indicates that α‐carbon of hydroxyl derivatives of beta diketones become stronger acids than the α‐carbon of beta diketone itself as their conjugate bases gain more stability via both enolate and hydrogen bond formation. Natural bond orbital and quantum theory of atoms in molecules analyses also confirm the role of hydrogen bond interactions on increasing the acidity of α‐carbon of hydroxyl derivatives of beta diketones. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to investigate the acidity of the various silica alkyl sulfonic acids. In this regard, cluster models with various alkyl spacer lengths were selected to mimic the surface of silica gel. The effects of distance from the surface and the role of hydrogen bond (H–bond) on the ΔHacidityvalues of these catalysts were investigated. DFT calculations revealed that a notable gap of ΔHacidityvalues exists between the structures considering lateral hydrogen bonding with the surface of the silicaHB structureand the structures with omitted surface interactions (non-HB structures). Natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses were carried out to obtain detailed information about the nature of the H–bonds. [ABSTRACT FROM AUTHOR]

In this study, the drastic influence of the boron atom on the acidity of alcohol has been con-sidered. The calculated ΔHacid (320.9--338.1 kcal/mol) and pKa range of boron containing alcohol (--0.1--9.4) indicate that the boronation of alcohol leads to considerable enhancement of its acidity. For instance, we have obtained the ΔHacid values 338.1, 335.2 kcal/mol and the pKa values 4.12, 2.81 for BH2CH2OH, BF2CH2OH alcohols, respectively, which are much smaller than that of CH3OH (with ΔHacid = 374.9kcal/mol and pKa = 15). The increase in the acidity of boronated alcohol can be related to the stabilization of alkoxy ion due to overlap of unoc-cupied orbital of boron atom with the electron pairs of negative oxygen. All gas phase computations were performed at MP2/6-311++G(d,p)//(B3LYP/6-31+G(d)) level. The primary results indicate that the presence of boron atom in an alcohol might make it as acidic as nitric acid. The geometry optimization of studied structures was performed with DFT computation and optimized structures were used to carry out natural bond orbital (NBO) analysis. NBO analysis revealed that the increase in the acidity of boron-containing alcohols is due to the charge transfer from the negative oxygen (in deprotonated structure) to the empty orbital of --BH2 and --BF2. Quantum theory of atoms in molecules (QTAIM) was also applied to determine the nature of bonds formed in the deprotonated structure. [ABSTRACT FROM AUTHOR]