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

Abstract

The acidity constants of molecular acid, K a (HA), cationic acid, K a (BH + ), as well as the equilibrium constants of anionic homoconjugation, K AHA − , cationic homoconjugation, K BHB + , and molecular heteroconjugation, K AHB , have been determined in (n-butylamine + acetic acid) systems without proton transfer in binary [dimethyl sulfoxide (DMSO) + 1,4-dioxane (D)] solvent mixtures. The constants were determined by using the potentiometric titration method at a fixed ionic strength. It is concluded that the molecular heteroconjugation constants in the mixed solvent systems studied are linearly related to the 1,4-dioxane content. Furthermore, in the (acid + base) systems without proton transfer, the direction of titration (direct B + HA or reverse HA + B) has been found to affect the precision of determination of reliable values of molecular heteroconjugation constants. Moreover, it has been found that the relative dielectric constants of the solvent mixtures studied change linearly as a function of solvent composition, as well as solvent components do not show interactions of solvent-solvent type.

Impactful Role of Cocatalysts on Molecular Electrocatalytic Hydrogen Production

“…The observed current enhancement may be derived from the amines’ association to the metal center during catalysis or from its ability to form a heteroconjugate with AcOH. − We performed LSV titration experiments of TPPFe (1 mM) with 40 mM AcOH and increasing amounts of trimethylphosphite, P­(OMe) 3 , which may bind TPPFe­(II)–H weakly and is unlikely to form a heteroconjugate with AcOH. The results are shown in Figure along with corresponding LSV simulations, performed in the same manner as for the amines (see Figure S7 for LSV over the full potential range).…”