Qualitative Analysis of Clustering in Aqueous Alcohol Solutions

Abstract

The specific features of clustering in the aqueous solutions of monohydric alcohols with concentrations higher than that at the peculiar point are discussed. Clustering is a result of the formation of hydrogen bonds between water and alcohol molecules, the energy of which somewhat exceeds the energy of hydrogen bonds in the water-water and alcohol-alcohol molecular pairs. Elementary clusters are assumed to be formed, whose composition is fixed at the solution concentrations lower than that at the peculiar point and changes according to a certain law at higher concentrations. The solution clustering degree was determined as a function of the solution concentration and the temperature.K e y w o r d s: solutions, water, monohydric alcohols, elementary clusters, peculiar point. IntroductionThe properties of aqueous monohydric alcohol solutions differ substantially from the properties of ideal solutions [1][2][3]. This difference reveals itself in the optical properties of solutions, in particular, in the appearance of maxima in the abnormal light scattering [4][5][6], in the form of the concentration and temperature dependences of the adiabatic compressibility [7] and the heat capacity [8], in the emergence of large relaxation times [2,9] and other features in the volumetric behavior of those solutions [10,11], in particular, their contraction [12][13][14].The first models of solutions as associated systems were developed by D.I. Mendeleev more than 150 years ago after the systematic studies of clustering in water-alcohol solutions [15]. This concept was developed and detailed in further researches, both experimental and theoretical ones, which had been reflected in a number of reviews [1,16]. In particular, Scatchard [17], using thermodynamic methods, studied the volume change at the solution formation from its components.In works [12][13][14], the manifestation of clustering in the behavior of the simplest solution characteristic,

Qualitative Analysis of Clustering in Aqueous Alcohol Solutions. II

“…This statement obviously contradicts the division of the concentration interval into a number of sections, which was proposed in work [32]. In particular, these are sections 1) 0 ≤ ≤ 0.0766, where the solution consists of associates of the first type ( As was done earlier [31], let us assume the solution volume to consist of the water and alcohol volumes (…”

“…To the right from the singular point, the number of water molecules is not enough for the formation of elementary clusters. As a result, the behavior of the parameter was modeled in work [31] by the expression…”

“…Taking the results obtained in work [31] into account, the relation between the parameter a ( , ) and the solution contraction ( , ) is given by the formula…”

“…a / a . The behavior of the parameter a ( , ) in the concentration interval p < < 1 was determined in work [31].…”

Якісний Аналіз Кластеризації В Спиртово-Водних Розчинах III

“…The clustering in aqueous alcohol (methanol and ethanol) solutions in the concentration intervals 𝑥 𝑝 𝑥 1 [8] and 0 𝑥 𝑥 𝑝 [9], where 𝑥 𝑝 is the molar fraction of the alcohol corresponding to the special solution point [10][11][12][13], was considered in works [8,9]. The aqueous alcohol solution is considered as a mixture of three components (substances): water, alcohol, and clusters formed by the alcohol and water molecules.…”