Equilibrium solubility, model evaluation and molecular dynamic simulation of riluzole in three binary solvents from 278.15 K to 323.15 K

Abstract

In this paper, it was measured that the solubility of riluzole in three binary mixtures ((ethanol/n-propanol/acetone) + H2O) through the method of laser monitoring under 278.15–323.15 K and 0.1 MPa. As expected, the solubility of riluzole in three binary solvents increases with rising temperature. For the acetone + water system, the solubility of riluzole increases monotonously with the increasing mass fraction of acetone. For the ethanol + water system, the solubility order is: ethanol (ω1 = 0.8999) > ethanol (ω1 = 0.7999) > ethanol (ω1 = 0.5999) > ethanol (ω1 = 0.7000) > ethanol (ω1 = 0.5000) > ethanol (ω1 = 0.4000). For the n-propanol + water system, the solubility order is: n-propanol (ω1 = 0.8000) > n-propanol (ω1 = 0.8998) > n-propanol (ω1 = 0.6999) > n-propanol (ω1 = 0.6000) > n-propanol (ω1 = 0.4999) > n-propanol (ω1 = 0.4000) > n-propanol (ω1 = 0.2999). The above phenomenon shows that when the mass fraction of ethanol is 0.5999 and the mass fraction of n-propanol is 0.8000, co-dissolution may occur. The solubility data were correlated via five models (modified Apelblat model, λh model, NRTL model, Uniquac model and Wilson model). As a result, we found that the modified Apelblat model has the most satisfactory correlation. Finally, the radial distribution function (RDF) obtained from molecular simulation were employed to analyze the solubility sequence of riluzole in more depth.