Dissociation equilibria of picric acid in the binary N, N-dimethylformamide/2-methoxyethanol solvent system

Abstract

Three empirical equations are proposed to fit the experimental values of the dissociation constant for picric acid, chosen as guide-solute working in the N, N-dimethylformamide/2-methoxyethanol solvent system. The work was performed operating at 19 temperatures ranging from − 10 to + 80 °C in the pure solvents and in their nine mixtures, identified by the mole fraction (X) of one component. This empirical treatment, which describes the dependence of the dissociation constant on temperature and composition of the solvent mixture, is represented by functions of the type K = K(T), K = K(X), and K = K(T, X). The K = K(T, X) equation in its complete form is composed of 20 terms, some of which can be eliminated because of small statistical weight; the number and type of these terms vary on passing from one solvent system to another and the best-fitting form is suggested. A comparison among various K = K(T, X) equations proposed in the present and in previous works has been made. Key words: dissociation equilibria, binary nonaqueous solvent mixtures, picric acid, N,N-dimethylformamide, 2-methoxyethanol.

Static dielectric constants of the N,N-dimethylformamide/2-methoxyethanol solvent system at various temperatures

“…Thus we only needed to determine two coefficients a , and b,, which are the true adjustment parameters (Table I11 of supplementary material). 2 The experimental E values in Table 2 are reproduced with an average uncertainty of f 0 . 0 2~ unit.…”

“…In a recent paper, we reported the dissociation constant of picric acid, obtained experimentally using the conductometric method under the same experimental conditions as above (2). N, N-Dimethylformamide is a nonaqueous solvent of particular interest because it has no hydrogen bonding in the pure state.…”

Relative permittivity of 1,2-ethanediol + 1,2-dimethoxyethane from -10 to +30.degree.C

“…At first, we have Investigated the binary solvent systems composed of 1,2-ethanedlol, 2-methoxyethanol, N,N'-dlmethylformamlde, and water, crossing the components with each other, and In a wide temperature range (1)(2)(3)(4)(5). In this way, It Is possible to elucidate some peculiarities of the selected solute/sotvent systems because the chosen binary mixtures make possible the variation "in continuum" of the extrathermodynamic parameters such as density, viscosity, relative permittivity, and any other Intensive chemlcophyslcal properties of liquids that Influence the real behavior.…”

“…(4) for apparatus 1, Flgulére et al (5) for apparatus 2, Fontalba et al(6) for apparatus 3, and Laugler and Rlchon (7) for apparatus4. …”