Thermodynamics of 1-alkanol + linear polyether mixtures Juan Antonio González ⇑ , Ángela Mediavilla, Isaías García De la Fuente, José Carlos Cobos G.E.T.E.F., Departamento de Física Aplicada, Facultad de Ciencias, Universidad de Valladolid, 47071 Valladolid, Spain article info Article history: Received 3 October 2012 Received in revised form 20 November 2012 Accepted 6 December 2012 Available online 31 December 2012 Keywords: 1-Alkanol Polyether Calorimetric data Volumetric data Interactions Dipolar Flory abstract Experimental densities, q, and speeds of sound, u, have been measured at (293.15–303.15) K for the sys- tems methanol, 1-butanol or 1-decanol + 3,6,9-trioxaundecane using a vibrating-tube densimeter and sound analyzer Anton Paar model DSA-5000. These values were used to calculate excess molar volumes, V E m , excess adiabatic compressibilities, j E S , and excess speeds of sound, u E . Data available in the literature on excess molar enthalpies, H E m , and on excess molar isobaric heat capacities, C E p;m , of 1-alkanol + linear polyether mixtures indicate that: (i) interactions are mainly of dipolar type, particularly for solutions with longer 1-alkanols; (ii) the ability of the ether to break the alcohol self-association increases with the number of CH 2 CH 2 O groups in the oxaalkane. The enthalpies of the alcohol-ether interactions, DH OHO , have been determined. In mixtures with a given polyether, DH OHO increases with the alcohol size. For 1-alkanol + CH 3 O(CH 2 CH 2 O) n CH 3 systems, DH OHO decreases for increased n values. Alcohol- ether interactions are stronger in mixtures with linear polyethers than in those with monoethers.V E m data show the existence of free volume effects in solutions including methanol or ethanol. These effects become more important for large n values, which is supported by values of @V E m @T  P . The Flory model has been used to investigate orientational effects in the systems under study. It is shown that orienta- tional effects are relevant in mixtures with methanol or ethanol, and that the behaviour of the remaining systems is close to that of random mixing. Solutions with 3,6-dioxaoctane slightly differ from this trend and are characterized by weak orientational effects. We have also applied the Flory model to 1-alka- nol + PEG-250, or +PEG-350 mixtures, which behave similarly to those including linear polyethers. Orien- tational effects are much stronger in 1-alkanol + linear monoether systems, and are roughly independent of the mixture components. Results obtained in this work are consistent with those obtained previously when applying the Kirkwood–Buff formalism. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Interest on alcohol + ether mixtures is consequence of their wide variety of applications. This type of systems is used as gasoline addi- tives due to their octane-enhancing and pollution reducing proper- ties [1,2]. Solutions of alcohols (refrigerant) with absorbents as polyethers or polyethylene glycols (PEG) have been proposed as working fluids for absorption refrigerant machines in order to im- prove the cycle machine [3]. Alkanol + ether mixtures are industri- ally relevant because alkanols are basic components in the synthesis of oxaalkanes and therefore are contained as an impurity. Mixtures of short chain 1-alkanols with linear polyethers are also interesting as can be considered as simple models of the complex systems water + PEG, widely used in biochemical and biomedical processes [4]. From a theoretical point of view, the study of 1-alka- nol + ether mixtures is particularly important due to their complex- ity, related to the partial destruction of the H-bonds between alcohol molecules by the active ether molecules, and to the new OH–O bonds created upon mixing [5,6]. On the other hand, in solu- tions formed by 1-alkanol and a linear polyether, strong dipole-di- pole interactions can be expected. Note the rather high upper critical solution temperatures of the mixtures 2,5,8,11-tetraoxad- odecane + dodecane or of 2,5,8,11,14-pentaoxapentadecane + dec- ane (280.81 K and 291,98 K, respectively [7]). This may explain that, in order to attain a better representation of the thermody- namic properties of the 1-propanol + 2,5,8-trioxanonane, or +2,5,8,11-tetraoxadodecane systems by means of the ERAS model [8], these polyethers were treated as self-associated compounds [9]. The present work is part of a general experimental and theoret- ical investigation on 1-alkanol + linear or cyclic polyether mix- tures. Thus, we have provided excess molar volumes, V E m , [10–14] and enthalpies, H E m [15–17] for this type of systems. In addition, we have investigated solutions of methanol, ethanol or 1-propanol with some linear or cyclic polyethers [18] using the Kirkwood–Buff formalism [19]; and 1-alkanol + 1,3-dioxolane, or +1,3-dioxane, or +1,4-dioxane, or +1,3,5-trioxane systems [6] in terms of the DIS- QUAC [20] and ERAS models. It should be mentioned that we have also developed detailed studies on 1-alkanol + linear or cyclic monoether mixtures using different theories (DISQUAC, ERAS, 0021-9614/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jct.2012.12.007 ⇑ Corresponding author. Tel.: +34 983 423757; fax: +34 983 423136. E-mail address: jagl@termo.uva.es (J.A. González). J. Chem. Thermodynamics 59 (2013) 195–208 Contents lists available at SciVerse ScienceDirect J. Chem. Thermodynamics journal homepage: www.elsevier.com/locate/jct