Hydrogen bonding. Part 25. The solvation properties of methylene iodide

Abstract

Ostwald solubility coefficients, L, have been determined for 37 gases and vapours in methylene iodide at 298 K, and have been correlated through equation (i), where the solute explanatory log L=–0.74 + 0.32R₂+ 1.34π₂^H+ 0.83α₂^H+ 1.19β₂^H+ 0.87 log L¹⁶(i) variables are R₂ an excess molar refraction, π₂^H the solute dipolarity/polarisability, α₂^H and β₂^H the solute hydrogen-bond acidity and basicity, and log L¹⁶ where L¹⁶ is the solute Ostwald solubility coefficient on hexadecane at 298 K. Similar equations have been constructed for solvation of solutes in tetrachloromethane, trichloromethane and 1,2-dichloroethane using literature data. It is shown that polarisability effects favour solvation in methylene iodide, through the R₂ term, but that such effects enhance the solubility of polarisable solutes only moderately: thus the R₂ term contributes 0.4 log units more in methylene iodide than in trichloromethane for the solute benzene. Examination of ΔG°, ΔH° and ΔS° for solvation of gaseous solutes suggests also that polarisability effects in methylene iodide are not very much larger than in the other halogenated solvents.