Enthalpies of crystalline fumaric, maleic and glutaric acids dissolution in water and aqueous solutions of potassium hydroxide at 298,15 k

Physicochemical study of dicarboxylic acids solutions is of great interest as they can be considered as model analogs of more complex biological systems. Data on thermodynamic characteristics of solutions of these compounds are required in different areas. The application of these compounds is extensive enough as they are widely used in pharmacy, medicine, food industry and polymers manufacturing. Moreover, they are necessary to develop, justify and optimize the processes involving these compounds.

Preparations of fumaric, maleic and glutaric acids of chemically pure grade were used. The goal of the current work was to define standard enthalpies of the formation of maleic, fumaric and glutaric acids in an aqueous solution, the enthalpy of dicarboxylic acid solution in water and aqueous solutions of KOH at the temperature of 298.15 K being considered.

The purity of the reagents was determined by potentiometric titration and appeared to be 99,7-99,9%. KOH and HNO3 solutions were prepared from reagents with ‘reagent grade’ qualification. The solution concentration was adjusted mainly by titrimetric methods. Calorimetric measurements were performed in ampoule calorimeter with an isothermal cover, thermistor temperature sensor KMT-14 and over time automatic recording of temperature changing. The operation of the calorimeter was verified by conventional calorimetric standards, mainly by the dissolution heat of crystalline potassium chloride in water.

The confidence interval of the mean AH value was calculated with a probability of 0.95, the equilibrium composition of solutions being obtained using RRSU program.

The values of standard enthalpies of fumaric, maleic, and glutaric acids formation and the products of their dissociation in aqueous solutions are key values in thermochemistry of these acids that opens the possibility of rigorous thermodynamic calculations in systems with these compounds.

In future, we are planning to investigate lanthanides complexation processes, gly-gly-gly being used as bioligand. We are hoping to study specific structures and the existence of isomers in compounds at enthalpy dissolution.

Skvortsov I. A.