Hydrogen Bonding between Solutes in Solvents Octan-1-ol and Water

Abstract

1:1 Equilibrium constants, K, for the association of hydrogen bond bases and hydrogen bond acids have been determined using solvent octan-1-ol at 298 K for 30 acid-base combinations. The values of K are much smaller than those found for aprotic, rather non-polar solvents. It is shown that the log K values can satisfactorily be correlated against αH2*βH2, where αH2 and βH2 are the 1:1 hydrogen bond acidities and basicities of solutes. The slope of the plot, 2.938, is much smaller than those for log K values in the non-polar organic solvents previously studied. An analysis of literature data on 1:1 hydrogen bonding in water yields a negative slope for a plot of log K against αH2*βH2, thus showing how the use of very strong hydrogen bond acids and bases does not lead to larger values of log K for 1:1 hydrogen bonding in water. It is suggested that for simple 1:1 association between mono-functional solutes in water, log K cannot be larger than about −0.1 log units. Descriptors have been obtained for the complex between 2,2,2-trifluoroethanol and propanone, and used to analyze solvent effects on the two reactants, the complex, and the complexation constant.

Summation Solute Hydrogen Bonding Acidity Values for Hydroxyl Substituted Flavones Determined by NMR Spectroscopy

“…From a plot of 1/(δ o -δ F ) versus 1/[D] o , the value of K was determined to be 12.2 M -1 . This corresponded to a value of 0.60 for α H 2 , which compared well with the reported value of 0.596 [35]. The estimate of δ B (9.00 ppm) was slightly less than the measured value of δ D (9.31 ppm).…”

“…The values of constants m and c are solvent specific and for chloroform these were recently reported to be 4.697 and -1.1, respectively [35]. The term β H 2 is the solute hydrogen bonding basicity of DMSO that has been reported as 0.775 [35,36]. Several assumptions were made in using Equation 6 to calculate α H 2 from the estimated value of K: 1) the values of m and c for chloroform were assumed to be the same as those for CDCl 3 , 2) the values of m and c for CDCl 3 were assumed to be unchanged in the presence of 0.10 M to 2.0 M DMSO-d 6, and 3) the value of β H 2 for DMSO-d 6 was assumed to be the same as for DMSO.…”

“…The values of constants m and c are solvent specific and for chloroform these were recently reported to be 4.697 and -1.1, respectively [35]. The term β H 2 is the solute hydrogen bonding basicity of DMSO that has been reported as 0.775 [35,36].…”

The lipophilicity and hydrogen bond strength of pyridine-N-oxides and protonated pyridine-N-oxides

“…For pyridine-N-oxide, 4-methyl-and 4-phenyl-pyridine-N-oxide there were just enough data to obtain the four unknown descriptors S, A, B and L. The A-values so obtained for the three compounds together with the A-value for 4-nitropyridine-4-oxide could be correlated with the R resonance parameter 15 to at least give an indication of the A-value that could be expected for other 4-substituted compounds, eqn (7). We use the symbol Res in eqn (7) to avoid confusion with the correlation coefficient. The Res parameter gives a measure of the resonance effect of a 4-substituent in stabilising the positive charge on the nitrogen atom.…”

A generalized G-SFED continuum solvation free energy calculation model

“…3; Abraham's parameters, adapted to represent the hydrogen-bond acidity and basicity of solute and solvent molecules, were developed only for solute molecules, and c a and c d in Eq. 5 are variables of solvent properties (65,66). Overall, G-SFED shows consistent accuracy for both small nonpolar and large multipolar molecules.…”