Excess partial molar enthalpies of alkane-mono-ols in aqueous solutions

Abstract

Excess partial molar enthalpies, H,~, of methanol, ethanol, and 1-and 2-propanols in aqueous solutions were measured directly, accurately, and in small increments in mole fraction at 25OC. From these data, the solute-solute enthalpic interactions, HAAE = N(aHAE1a~zA), were evaluated for each alcohol. These data indicate that three distinctively different mixing schemes, I, 11, and I11 exist, as was the case for aqueous 2-butoxyethanol previously studied in our laboratory. The transition from mixing scheme I to I1 appears to take place gradually within a small composition range. As the hydrophobic moiety becomes smaller from 2-butoxyethanol to methanol, the locus of the transition moves to a higher value in mole fraction of the alcohol. At the same time, the range of transition becomes wider and the solute-solute enthalpic interaction weaker.Key words: excess partial molar enthalpies in aqueous solutions, methanol, ethanol, I-propanol, 2-propanol, enthalpic interaction, transition of mixing scheme. Ces donnCes suggkrent l'existence de trois schCmas diffirents de mClanges, I, I1 et 111, comme ce ftit le cas pour le 2-butoxyCthanol CtudiC antkrieurement dans notre laboratoire. I1 semble que la transition du schCma de melange I vers I1 se produit graduellement, B I'intCrieur d'une faible plage de composition. Quand les portions hydrophobes deviennent plus petites en allant du 2-butoxyCthanol vers le mCthanol, le foyer de la transition se dCplace vers des valeurs plus ClevCs de la fraction molaire de l'alcool. En m&me temps, l'intervalle de transition devient plus grand et l'interaction enthalpique solutC-solutC devient plus faible.Mors clis : enthalpies molaires partielles en excks en solutions aqueuses, mCthanol, ethanol, propan-1-01, propan-2-01, interaction enthalpique, schCma de transition de melange.

Interactions in 1-Propanol−(1,2- and 1,3-)Propanediol−H2O: The Effect of Hydrophobic vs Hydrophilic Moiety on the Molecular Organization of H2O

“…9,10 Due to enthalpy-entropy compensation prevalent in aqueous solutions, 11 the x 1P -dependence of S 1P E and S 1P-1P E are similar to that of H 1P E and H 1P-1P E , particularly so in the water-rich region of our interest. We know from previous works on binary aqueous monools, 9,10,[12][13][14][15] that in the water-rich region what we call Mixing Scheme I is operative which is qualitatively different from mixing schemes in other regions. Mixing Scheme I is basically to protect the integrity of H 2 O by enhancing the hydrogen bond network in the immediate vicinity of solute ("iceberg formation").…”

“…12 Thus, the presence of 2P brings about the same modification to H 2 O as 1P would have done and additional 1P works the rest of the way to drive the system to Mixing Scheme II. Therefore the x 1P -dependence of H 1P-1P E must keep its same shape but be shifted in a parallel fashion to a smaller value of x 1P (to the left in Figure 7) as the initial mole fraction of 2P, x 2P 0 , increases.…”

Excess molar enthalpies for binary mixtures of n-propanol, acetic acid, and n-propyl acetate at 313.15K and atmospheric pressure

“…15, 293.15, 298.15, 303.15, 323.15 K and others) using different types of calorimeters, such as Tian-Calvet calorimeter, flow-mixing calorimeter, solution calorimeter, etc. [8][9][10][11][12][13][14][15][16][17][18][19]. A little less studied binary mixture is AcOH + H 2 O, its heats of mixing were measured at, for example, 296-298, 298.…”

Influence of the Mixing State of tert‐Butyl Alcohol‐water Mixtures on the Conformation of Bovine Serum Albumin

“…7,8 In spite of a large number of studies the mechanism of alcohols affecting the stability and solubility of proteins remains unresolved [3][4][5][6][7][8] due to the complex microstructure of the alcohol-water mixtures. [9][10][11][12][13][14][15] By far, little attention was paid to the relationship between the microstructure of alcohol-water mixtures and the conformation of proteins.…”

“…The TBA-water mixture is characterized by the anomalous physicochemical properties 9,10 and is considered as the typical compound to investigate the interaction of alcohols with proteins. [8][9][10][11][12][13][14][15] Recently, a variety of spectroscopic techniques including IR, 11 dynamic light scattering, 12 X-ray scattering 13 and neutron diffraction, 14 and theoretical approaches 15 have been used to reveal the microscopic structure of aqueous solutions of TBA and provide a new insight into the anomalous properties of the solutions at a molecule level.…”