Excess Chemical Potentials and Partial Molar Enthalpies in Aqueous 1,2- and 1,3-Propanediols at 25^°C

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• 作者：Parsons ; Matthew T. ; Lau ; Frankie W. ; Yee ; Eric G.M. ; Koga ; Yoshikata
• 关键词：Mixing schemes in aqueous 1 ; 2 ; and 1 ; 3 ; propanediols ; partial molar enthalpies ; chemical potentials ; interaction functions
• 刊名：Journal of Solution Chemistry
• 出版年：2003
• 出版时间：2003
• 年：2003
• 卷：32
• 期：2
• 页码：137-153
• 全文大小：98 KB

文摘

Excess chemical potentials and excess partial molar enthalpies of 1,2- and 1,3-propanediols (abbreviated as 12P and 13P), μ^E_i, and H^E_i (i = 12P or 13P) were determined in the respective binary aqueous solutions at 25^°C. For both systems, the values of μ^E_i are almost zero, within ±0.4 kJ-mol⁻¹. However, the excess partial molar enthalpies, H^E_i show a sharp mole fraction dependence in the water-rich region. Thus, the systems are highly nonideal, in spite of almost zero μ^E_i. Namely, the enthalpy–entropy compensation is almost complete. From the slopes of the H^E_i against the respective mole fraction x_i we obtain the enthalpic interaction functions between solutes, H_i−i^E, (i = 12P or 13P). Using these quantities and comparing them with the equivalent quantities for binary aqueous solutions of 1-propanol (1P), 2-propanol (2P), glycerol (Gly), and dimethyl sulfoxide (DMSO), we conclude that there are three composition regions in each of which mixing schemes are qualitatively different. Mixing Schemes II and III, operative in the intermediate and the solute-rich regions, seem similar in all the binary aqueous solutions mentioned above. Mixing Scheme I in the water-rich region is different from solute to solute. 12P shows a behavior similar to that of DMSO, which is somewhat different from typical hydrophobic solute, 1P or 2P. 13P, on the other hand, is less hydrophobic than 12P, and shows a behavior closer to glycerol, which shows hydrophilic behavior.