Potentiometric investigations of (acid+base) equilibria in (n-butylamine+acetic acid) systems in binary (acetone+cyclohexane) solvent mixtures

A potentiometric study of molecular heteroconjugation equilibria in (n-butylamine+acetic acid) systems in binary (acetonitrile +1,4-dioxane) solvent mixtures

“…For instance, for the (B + HA) and (AH + B) systems they amount to 1.89 (0.32) and 1.92 (0.43), respectively. This conclusion is compatible with that reached from measurements carried out in (n-butylamine + acetic acid) systems in binary (acetone + cyclohexane) solvent mixtures [26].…”

Molecular Heteroconjugation Equilibria in (n-Butylamine + Acetic Acid) Systems in Binary (Dimethyl Sulfoxide + 1,4-Dioxane) Solvent Mixtures

“…For the case of the reverse (HA + B) systems, all the molecular heteroconjugation equilibrium constants are associated with large-standard deviations and can be regarded as being virtually indeterminable. For comparison K AHB obtained in AC is 2.30 [24]. Similarly, in our previous paper [32] molecular heteroconjugation equilibrium constants were also determined by potentiometric titration for substituted phenol + n-butylamine systems in DMSO, which range from 2.77 to 5.32 on a logarithmic scale.…”

“…It can thus be concluded that in the (DMSO + D) mixed solvents the precision of the determination of molecular heteroconjugation equilibrium constants depend on the direction of titration. The binary solvent systems studied enable differentiation of the determinability of the molecular heteroconjugation equilibrium constants, unlike the previously studied (acetone + cyclohexane) [24] and (acetonitrile + 1,4-dioxane) [19] systems. In these systems only a qualitative indication for a determinability of the molecular heteroconjugation equilibrium constants in the direct (B + HA) systems could be obtained.…”

“…Acetic acid and n-butylamine were purified as usual [22], and auxiliary materials were obtained as described previously [23]. The detailed description of our laboratory equipment for potentiometric titrations, as well as the experimental procedure could be found in one of our previous papers [19,20,23,24].…”

Theoretical Studies of Interactions between O-Phosphorylated and Standard Amino-Acid Side-Chain Models in Water

“…19–23 The contribution of a salt bridge to protein stability has been investigated experimentally 19,20 and theoretically. 21–27 A number of theoretical studies are concerned with the strength of the hydrogen bonds involving phosphorylated amino-acid side chains. In particular, Mandell and co-workers, 28 and Masunov and Lazaridis 29 used molecular dynamics simulations to estimate the free energies of salt bridges between all charged standard amino-acid side chains in the most convenient orientations.…”