Third derivative thermodynamic quantities of aqueous tetrahydrofuran at 25 °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, δTHFSV, 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].