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Intermolecular interactions in 2-butoxyethanol-DMSO-H2O

TitleIntermolecular interactions in 2-butoxyethanol-DMSO-H2O
Publication TypeJournal Article
Year of Publication1996
AuthorsWesth, P, Koga, Y
JournalJournal of Physical Chemistry
Volume100
Pagination433-438
Date PublishedJan
Type of ArticleArticle
ISBN Number0022-3654
KeywordsAQUEOUS 2-BUTOXYETHANOL, denaturation, DIMETHYL-SULFOXIDE, LYSOZYME, MIXING SCHEME, MIXTURES, NEUTRON-DIFFRACTION, PARTIAL MOLAR ENTHALPIES, VOLUMES, WATER-RICH REGION
Abstract

Excess partial molar enthalpy, H-B(E), and chemical potential, mu(B)(E), of 2-butoxyethanol (B) were determined in ternary mixtures of B, dimethyl sulfoxide (D), and H2O. The data were obtained in small enough mole fraction increments to evaluate the so-called interaction functions, partial derivative H-B(E)/partial derivative x(B), partial derivative H-B(E)/partial derivative x(D), partial derivative mu(B)(E)/partial derivative x(B), and partial derivative mu(B)E/partial derivative x(D). These interaction functions previously proved useful in elucidating the ’’mixing schemes’’ in binary aqueous solutions of B and D. For the binary mixtures, it was found that both B and D influenced H2O in the following manner: in the water-rich composition range (region I) within a certain threshold (x(B) < 0.0175 and x(D) < 0.28 at 25 degrees C), both solutes enhance the hydrogen-bonded network of water in their vicinity, and the mixtures retain the percolated nature of the network. At higher B or D concentrations (region II) a qualitatively different mixing scheme becomes operative. The results from this work suggest that, in the ternary mixtures, solute B and D influences the percolated hydrogen bond network of water competitively or cooperatively. The observed effects are in accordance with those characteristic of mixing scheme I in the binary mixtures, as long as the concentration of both solutes is within the threshold values. When either one of the solutes is concentrated beyond its threshold, mixing scheme II seems to set in. It was found that D diminished the positive (unfavorable) enthalpy of B-B interactions and that this effect was almost completely compensated by changes in interaction entropy. Hence, D had little net effect on the Gibbs energy of mutual B interactions, or in other words, D did not weaken the hydrophobic attraction between B molecules. Evaluation of ’’heterogeneous’’ B-D interactions in region I suggested that they were weaker than B-B interactions and governed by reorganization of water-water hydrogen bonding rather than interactions between specific groups in B and D. Some implications of these findings on cosolvent effects in aqueous solutions of biopolymers are discussed.

URL<Go to ISI>://A1996TN83900065