Characterization of solvent mixtures: preferential solvation of chemical probes in binary solvent mixtures of polar hydrogen-bond acceptor solvents with polychlorinated co-solvents

Abstract

The use of chemical probes for the characterization of chemical properties is explored for aprotic binary solvent mixtures. The solvatochromic indicators N,N-diethyl-4-nitroaniline, 4-nitroanisole, 4-nitroaniline and 4-nitrophenol were used to characterize binary solvent mixtures of a polar aprotic hydrogen-bond acceptor solvent (ethyl acetate, acetonitrile and dimethyl sulfoxide) with a polychlorinated hydrogen-bond donor solvent (chloroform or dichloromethane). The solvent parameters p*, a and b of the binary mixtures were calculated from the solvatochromic shifts of the indicators. In each case the degree of convergence for a solvent property values obtained from different probes was analyzed. Data obtained by using the non-polar solvatochromic indicator b-carotene are additionally presented. The behavior of the solvent systems was analyzed according to their deviation from ideality due to preferential solvation of the solutes and the complicated intermolecular interactions of the two components of the solvent mixture. The validity of the concept of an intrinsic absolute property of a solvent mixture and whether such a property can be defined by means of chemical probes is discussed. Theoretical equations (preferential solvation models) were used to compute the solvatochromic data. The results were analyzed and related to the solvent effects on some aromatic nucleophilic substitution reactions, comparing the application of single-and multiparametric treatments of solvent effects.

Solvent hydrogen bonding and structural effects on the reaction of 2‐halo‐5‐nitropyridines with parasubstituted anilines in dimethylsulfoxide/acetonitrile mixtures

“…Examination of the literature revealed that the effects of structure on S N Ar2 reactions have largely been reported 9–23. However, only very few attempts have been made to study on the effect of solvent on such reactions in a more systematic manner 24–30. Hence, in this article, the reaction of few parasubsutituted anilines with 2‐bromo‐5‐nitropyridine and with 2‐chloro‐5‐nitropyridine in dimethylsulfoxide (DMSO)/acetonitrile (AcN) (both polar, aprotic, Hydrogen Bond Acceptor, PAHBA solvents) mixtures of varying compositions has been reported.…”

Solvation model for acetic acid in binary mixtures of cyclohexane–1,2-dichloroethane

“…The n dependence of K dim,n could, therefore, be expressed by Eq. (11) K dim,n = K cyc dim (1 − n + 1.86n) 4 (1 − n + 6.91n) 4 (11) where the numerator represents the contribution of four solvation sites of the dimer and the denominator represents that arising from four solvation sites of the two monomeric entities. Substitution of appropriate n values in Eq.…”

“…and the specific solute-solvent interactions (hydrogen bonding). Despite the many theoretical [1,2] as well as experimental [3][4][5] approaches reported to elucidate this phenomenon, the general mechanisms of preferential solvation in mixed solvents has not yet been completely clarified.…”

Role of Hydrogen Bond in the Solvation Behavior of the Binary Mixtures Containing Fluorocarbon Alcohol Molecules and Chloroform: An Experimental and Theoretical Study

“…In other cases, both constituents of the solvent mixture can solvate a probe molecule as a different entity which provides a completely different solvation environment around the solute molecule causing to show a significant change of a particular property (solvation in the present study) from its bulk counterparts and this effect is known as synergetic effect . The experimental and theoretical tools have been used in a great deal to understand the preferential solvation as well as synergetic behavior of the solvent mixtures . Several different spectroscopic techniques such as UV‐Vis, NMR, vibrational spectroscopy, solvation dynamics, two dimensional infrared techniques have been used to understand the behavior of solvent mixtures as these techniques have the capability to provide the quantitative information about the solute‐solvent interaction as well as hydrogen bond network present in solvent mixtures.…”