2-Methoxy-4-nitroaniline Solubility in Several Aqueous Solvent Mixtures: Determination, Modeling, and Preferential Solvation

The main aim of this contribution was to report the solubility of 2-methoxy-4-nitroaniline in mixtures of isopropanol + water, ethylene glycol + water, n-propanol + water, and dimethyl sulfoxide (DMSO) + water. The solubility data in the mole fraction scale were obtained by means of the isothermal shake-flask method covering the temperature range of 278.15-323.15 K under local pressure (101.2 kPa). It presented a positive increase as the mass fractions of organic solvents increased. At the same experimental temperature and mass fractions of organic solvents, the solubility of 2-methoxy-4-nitroaniline (mole fraction) was greater in the DMSO and water mixture than in the other solvent mixtures. The equilibrated solid phases with their liquid phases were checked by way of X-ray power diffraction, presenting the absence of solvate formation and crystal transition during all experiments. The acquired solubility was fitted by means of three cosolvency models such as van't Hoff-Jouyban-Acree, Jouyban-Acree, and Apelblat-Jouyban-Acree. The back-calculated data were in good agreement with the experimental ones. The obtained magnitudes of relative average deviation and root-mean-square deviation were no more than 6.82% and 35.56 X 10(-4), respectively. The local mole fractions of organic solvents near 2-methoxy-4-nitroaniline were quantitatively calculated by the use of the inverse Kirkwood-Buff integral method. 2-Methoxy-4-nitroaniline was preferentially solvated by water in water-rich compositions, whereas in cosolvent-rich and intermediate compositions, 2-methoxy-4-nitroaniline was preferentially solvated by the organic solvent in the mixtures studied.