(685h) Temperature-Dependent Physicochemical Properties of Nitrotoluenes from Solvation Free Energies

The temperature-dependent vapor pressure, solubility, Henry’s law constant, and partition coefficients are important in many industrial applications and in environmental modelling. However, the reliable data for these properties are not always available, especially, for hazardous and exothermic compounds, such as the nitrotoluenes. Here we demonstrate how force field-based solvation and self-solvation free energies as functions of temperature can be used to compute a wide range of physicochemical solvation properties. The temperature-dependent solvation free energies in water, 1-octanol, and in the pure liquid or subcooled phases for a set of nitrotoluenes are computed using expanded ensemble molecular simulation method over the temperature range of 273 K to 330 K. TraPPE force field parameters with CHELPG charges were used to model the nitrotoluenes. TIP3P and TraPPE-UA force field parameters were used to model water and 1-octanol, respectively. Subcooled and liquid-phase vapor pressures, solubilities, Henry’s law constant, and partition coefficients (air-water, air-octanol, and water-octanol) are predicted and compared with available experimental data. The changes in entropy, enthalpy, and heat capacities are estimated both for the solvation of the solute in water and in 1-octanol, and for the transfer of the solute from water to 1-octanol. The effects of functional groups and molecular structure on physicochemical and thermodynamic properties are also discussed. The protocol followed here can be used for compounds for which temperature-dependent data are scarce or not accessible due to hazardous or exothermic nature.