Thermodynamics of solute transfer from water to hexadecane
New measurements of enthalpies of solution in hexadecane and in water (ΔH°s), and gas-hexadecane Ostwald solubility coefficients (LH) of neutral monomeric organic solutes are reported. These values, together with literature values of ΔHs°, LH, and gas-water Ostwald solubility coefficients (Lw), have been used to derive the Gibbs energies, enthalpies, and entropies of solute transfer from water to hexadecane (ΔG°tr′, ΔHtr′°, and ΔStr°), as well as water–hexadecane partition coefficients (as log PH). Results have been examined by the method of multiple linear regression analysis, using the equation, SP =c+dδ2+sπ2*+aα2+bβ2+vV2
The sπ2* term is difficult to interpret, but the aα2 and bβ2 terms can be shown to arise through hydrogen bonding of solute molecules to the bulk water that is exothermic but rather disfavoured entropically. It is shown also that thevV2 term arises due to a combination of cavity effects and general dispersion interactions in bulk water and bulk hexadecane.