Ultrasound speeds and molar isentropic compressions of aqueous 1-propoxypropan-2-ol mixtures from T = (283.15 to 303.15) K. Influence of solute structure

Ultrasound speeds were experimentally determined in 27 aqueous binary mixtures of 1-propoxypropan-2-ol (1-pp-2-ol) spanning the entire composition range and at temperatures between (283 and 303) K. Isentropic compressibilities were calculated by combining ultrasound speed and density data. Excess molar isentropic compressions were estimated. Excess partial molar isentropic compressions of both components and respective limits at infinite dilution were analytically obtained from Redlich-Kister fitting coefficients. Analysis of temperature and composition dependence of excess partial molar isentropic compressions, especially in the water-and 1-pp-2-ol-rich regions was carried out aiming to clarify changes in associative schemes along the entire composition range. The role of branching and chain length on mixing and especially on aggregation patterns was further investigated comparing the present results with those for isomeric 2-butoxyethanols, which are structural isomers of 1-pp-2-ol, and for 2-isopropoxyethanol. (C) 2011 Elsevier Ltd. All rights reserved.