A conductometric study of dissociation of picric acid in 2-methoxyethanol and 1,2-ethanediol from −10 to 80 °C

Abstract

GIANCARLO FRANCHINI, ELENA ON, CARLO PRETI, LORENZO TASSI, and GIUSEPPE TOSI. Can. J. Chem. 65, 722 (1987). Dissociation constants of 2,4,6-trinitrophenol (picric acid) in 2-methoxyethanol and 1,2-ethanediol were measured by a conductance method at temperatures ranging from -10 to 80°C. The determined constants in the two solvents are discussed and are compared on the basis of the physical properties of the solvents, which have been measured at the various temperatures. The dissociation constants show different behaviour with the temperature in the investigated range and they are fitted by equations of the type In K = A+BT+C/T+D In T . Furthermore, the thermodynamic functions have been evaluated and discussed.GIANCARLO FRANCHINI, ELENA ON, CARLO PRETI, LORENZO TASSI et GIUSEPPE TOSI. Can. J. Chem. 65, 722 (1987).Optrant a des temptratures allant de -10 a 80°C et faisant appel a la conductimttrie, on a mesurC les constantes de dissociation du trinitro-2,4,6 phtnol (acide picrique) dans le mCthoxy-2 tthanol et dans l'tthanediol-1,2. On discute des constantes dtterminies dans ces deux solvants et on les compare entre elles en fonction des propriCtCs physiques de ces solvants qui ont CtC mesurCes aux diverses temptratures. Dans la fourchette des tempkratures examintes, les constantes de dissociation prtsentent des comportements diffkrents que l'on peut toutefois reprtsenter par des tquations du type InDe plus, on a tvaluC et on discute des fonctions thermodynamiques.[Traduit par la revue] Introduction This work is to study the effect of solvent on dissociation constants of weak acids and the influence of temperature.Although alcohols have received much attention as solvents for acid-base determinations (1, 2) there are not many studies on the use of 2-methoxyethanol (hereafter abbreviated Gliem) and 1,2-ethanediol (Gliet) as solvents in acid-base titrations and on the determination of dissociation constants of weak acids. Our previous works (3-6) have reported on the feasibility of conductometric titrations of monoprotic and diprotic acids, phenols and aromatic nitroderivatives in the above solvents using N,N1-diphenylguanidine as titrant. The results indicated the possibility of also performing differential titrations of acid mixtures in cases where such determinations are impossible in aqueous solutions.Preliminary studies have shown that temperature plays an important role in the shape of the conductometric titrations curves and that the effect is different for different solvents.Continuing our conductometric studies, the dissociation constants of picric acid in Gliet and Gliem have been determined at different temperatures and the data obtained are discussed. The reaction under study in the two solvents is

The Audio Frequency Conductance Study of Some Metal Succinate Salts in Aqueous Medium at Different Temperatures (Part I: Magnesium, Manganese (II), Barium and Copper Succinates)

“…As a consequence, many complexes become signi�cantly stable at high temperatures [30]. e same trend was found by Franchini et al [31] for a conductometric study of dissociation of picric acid in two different organic solvents at different temperatures, as well as by Sokol et al [13] in their study for the thermodynamics of the association reaction conductance measurements.…”

The ethane-1,2-diol–water solvent system. The dependence of the dissociation constant of picric acid on the temperature and composition of the solvent mixture

“…4 reproduces some of these curves at different temperatures. The coefficients b, obviously represent the reverse case of the ai parameters and will contain an implicit dependence on temperature; in this case we may write bi = b,( T ) for j = 0,1,2,3,4 ( 5 ) which is a general expression.…”

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

“…Now, the trend among all the binary mixtures DMF/Gliem and Gliet/Gliem being the same, one may think that preferential or selective solvation of solute takes place and occurs in the DMF/Gliem solvent system through the molecules of DMF, which are more solvating than the Gliem molecules (20.03 5 e=liern 4 13.02 for -10 4 t("C) 4 80) (8).…”

“…In our previous papers, we reported the dissociation constants, evaluated by the conductometric method in the -10 to +80°C temperature range, of picric acid in 1,2-ethanediol (Gliet), 2-methoxyethanol (Gliem) (8), and their binary mixtures (9, lo), in the Glietlwater (1 1) and Gliemlwater (12) solvent systems.…”