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In this study, the drastic influence of the boron atom on the acidity of alcohol has been considered. 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 BH 2CH2OH, BF2CH2OH alcohols, respectively, which are much smaller than that of CH3OH (with ΔHacid = 374.9 kcal/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 unoccupied orbital of boron atom with the electron pairs... 

Density functional theory method and B3LYP/6-31+G(d) level of theory were used to predict the acidity of barbiturates and their corresponding metabolites in the gas and solution phase (H2O). Polarized continuum model was applied to calculate pKa values of barbiturates and metabolites. A comparison between acidity of barbiturates and metabolites in the gas and solution phase indicates that the acidity strength of barbiturates enhances with the increase of intramolecular hydrogen bonds in metabolites. This acidity can increase to 9.47 kcal/mol in gas phase and 2.73 pKa units in solution phase for a typical metabolite of barbiturate due to the effect of intramolecular hydrogen bonds. Also,... 

The pK a of an acyclic aliphatic heptaol ((HOCH 2CH 2CH(OH)CH 2) 3COH) was measured in DMSO, and its gas-phase acidity is reported as well. This tertiary alcohol was found to be 10 21 times more acidic than tert-butyl alcohol in DMSO and an order of magnitude more acidic than acetic acid (i.e., pK a = 11.4 vs 12.3). This can be attributed to a 21.9 kcal mol -1 stabilization of the charged oxygen center in the conjugate base by three hydrogen bonds and another 6.3 kcal mol -1 stabilization resulting from an additional three hydrogen bonds between the uncharged primary and secondary hydroxyl groups. Charge delocalization by both the first and second solvation shells may be used to facilitate... 

Hydrogen bonds are the dominant motif for organizing the three-dimensional structures of biomolecules such as carbohydrates, nucleic acids, and proteins, and serve as templates for proton transfer reactions. Computations, gas-phase acidity measurements, and pKa determinations in dimethyl sulfoxide on a series of polyols indicate that multiple hydrogen bonds to a single charged center lead to greatly enhanced acidities. A new class of Brønsted acids, consequently, is proposed. © 2009 American Chemical Society