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Excess chemical potentials and partial molar enthalpies in aqueous 1,2-and 1,3-propanediols at 25 degrees C

TitleExcess chemical potentials and partial molar enthalpies in aqueous 1,2-and 1,3-propanediols at 25 degrees C
Publication TypeJournal Article
Year of Publication2003
AuthorsParsons, MT, Lau, FW, Yee, EGM, Koga, Y
JournalJournal of Solution Chemistry
Volume32
Pagination137-153
Date PublishedFeb
Type of ArticleArticle
ISBN Number0095-9782
Keywords2-and 1, 3-propanediols, ALCOHOL, chemical potentials, ENERGIES, ENTHALPIES, ENTROPIES, H2O, interaction functions, MIXING SCHEMES, mixing schemes in aqueous 1, MOLECULAR-ORGANIZATION, NONELECTROLYTES, partial molar, TERT-BUTANOL MIXTURES, VOLUMES, WATER-RICH REGION
Abstract

Excess chemical potentials and excess partial molar enthalpies of 1,2- and 1,3-propanediols ( abbreviated as 12P and 13P), mu(i)(E), and H-i(E) ( i = 12P or 13P) were determined in the respective binary aqueous solutions at 25degreesC. For both systems, the values of mu(i)(E) are almost zero, within +/-0.4 kJ-mol(-1). However, the excess partial molar enthalpies, H-i(E) show a sharp mole fraction dependence in the water-rich region. Thus, the systems are highly nonideal, in spite of almost zero mu(i)(E). Namely, the enthalpy-entropy compensation is almost complete. From the slopes of the HE 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.

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