Third derivative thermodynamic quantities of aqueous tetrahydrofuran at 25 degrees C

We measured the excess chemical potential, μΕTHF, the excess partial molar enthalpy and entropy of solute tetrahydrofuran (THF), HETHF and SETHF, in THF–H2O at 25 °C. Using these second derivatives of G, we graphically evaluated the third derivative quantities; the enthalpic, entropic THF–THF interaction functions, HETHF–THF, and SETHF–THF. Using the literature density data, the effect of THF on the excess partial molar volume of THF, VETHF–THF, was also evaluated. Furthermore, we directly determined the partial molar entropy-volume cross fluctuation density of THF, View the MathML sourceδTHFSV, another third derivative quantity. By comparing the mole fraction dependence patterns of these third derivative quantities between the present THF–H2O with what we thought to be the weakest member of a hydrophobic mono-ol series, methanol (ME), we suggest that in spite of its larger non-polar surface area, THF is as amphiphilic as ME. A quantitative characterization and any difference between THF and ME ought to wait for characterization by the 1-propanol probing methodology developed by us [PCCP 15(2013) 14548-14565]