Partitioning properties of linear and branched ethers: Determination of linear solvation energy relationship (LSER) descriptors

Solute descriptors of linear solvation energy relationship (LSER) for dialkyl ethers were examined as a means for improving predictions of their fate and behavior in the environment. LSER solute descriptors consist of the excess molar refraction, the polarizability/dipolarity parameter, the effective hydrogen (H)-bond acidity/basicity, McGowan's characteristic volume and the hexadecane–air partitioning coefficient. Descriptor determination was done based on partitioning coefficients measured in this study for six alkyl ethers including linear and branched compounds. Calibration of the solute descriptors revealed that the effective solute H-bond basicity of branched ethers is significantly higher than that of linear ethers, which has been neglected in previous LSER studies. Revised solute descriptors accurately calculated measured partitioning coefficients in most systems. The inspection of solute H-bond basicities of ethers in different solvent–water and solvent–air systems suggested that the H-bond basicity of an ether can vary depending on the solvent in which the ether dissolves. Neglecting this donor-dependency of the H-bond basicity could lead to significantly poorer estimations by the LSER, when the solvent or sorbent of concern is a strong H-bond acid. Other H-bond basic compounds possibly pose a donor-dependent basicity as well.