The Solvent Dimethyl Sulfoxide

The H,,, H r , and (in part) the H A acidity functions have been determined in 70% DMSO-water for the sulfuric acid concentration range 0-85%. In sharp contrast to purely aqueous acid systems the H, (primary aniline) and H r (tertiary aniline) scales in DMSO-water are closely parallel over a wide range of acidity. This provides clear experimental demonstration that linearity of log (ionization ratio) us. acidity function with unit slope is not a sufficient condition that a base is obeying a given acidity function. When the three acidity functions in DMSO-water are shifted to a purely aqueous standard state, their order is completely reversed from that observed in aqueous acids. These differences in behavior are discussed in terms of cation solvation by DMSO molecules only. Les fonctions d'acidite H,, H;", et (en partie) HA, ont ete determinees dans un melange a 70% DMSO-eau pour des concentrations en acide sulfurique allant de 0 i 85%. A I'encontre des systemes acides purement aqueux, les echelles H, (aniline primaire) et H r (aniline tertiaire) sont, dans le DMSO-eau, etroitement paralleles sur une vaste Cchelle d'acidite. Ceci constitue une bonne preuve experimentale d'apres laquelle la linearite du log (rapport d'ionisation) par rapport a la fonction d'acidite avec une pente unitaire ne constitue pas une condition suffisante pour affirmer qu'une base obeit a une fonction d'aciditk donnee. Lorsque les trois fonctions d'acidite dans le DMSO-eau sont deplacees vers un Ctat standard purement aqueux, leur ordre est completement inverse par rapport a celui observe en milieu acide aqueux. Ces differences de comportements sont rationalisees en termes d'une solvatation cationique par les seules molecules de DMSO.

Section: Introductionsupporting

confidence: 87%

Acidity Function Behavior in Aqueous-organic Solvents. I. The H₀, and H_A Functions in 70% DMSO–H₂O

Yates¹,

Welch²

1972

“…The high purity of the distilled liquid was confirmed by melting point (18.52 "C, lit: 18.55 "C (3)) and refractive index (nDZ0 = 1.3590, lit: nD19.4 = 1.35886 (3)). …”

Section: Methodsmentioning

confidence: 99%

Partial molal volume behavior of tetraalkylammonium chlorides in aqueous acetone and aqueous dimethylsulfoxide

Macdonald¹,

Hyne²

1970

The partial molal volumes of a series of tetraalkylammonium chlorides in aqueous acetone and aqueous dimethylsulfoxide at 25.000 "C are reported as a function of solvent composition. It is shown that for each solvent composition the partial niolal volume data are better represented by a quadratic in solute molecular weight than by the linear expression previously employed in similar studies. Extrapolation of molecular partial molal volumes to zero cation molecular weight has permitted evaluation of the partial molal volumes of the ions R4N+ and C1-. The variation of molecular and ionic partial molal volume as a function of solveht composition is discussed.

“…Gibson and Loeffler (17, 18) and others (19) postulate that where classical mechanics are applicable, the total energy of a fluid may be regarded as the sum of three terms; (a) the mean kinetic energy of the molecules at their equilibrium positions including the energy associated with rotation or internal degrees of freedom, U(T); (6) the potential energy due to attractive intermolecular forces, UA; and (c) due to repulsive forces UR.…”

Section: Energy-volume Coeficientsmentioning

confidence: 99%

The Thermal Pressure and Energy–Volume Coefficients of Dimethyl Sulfoxide – Water Mixtures

Macdonald¹,

Hyne²

1971

Thermal pressure and energy-volume coefficients are reported for several DMSO-water mixtures over the temperature range 13-55 "C. The energy-volume coefficient at 25 "C is found to pass through a maximum at 0.3-0.4 mole fraction DMSO and this observation is rationalized in terms of maximization of intercomponent interactions. The relationship between the energy-volume coefficient and the cohesive energy density of the binary liquid system is examined. The temperature dependence of the thermal pressure coefficient is discussed in terms of the effect of temperature on the susceptibility of the entropy of DMSO-water mixtures to isothermal expansion. Canadian Journal of Chemistry, 49, 611 (1971) IntroductionIn this paper we report the energy-volume Dimethylsulfoxide (DMSO) -water mixtures have been used extensively as solvent media for kinetic studies ( 1 4 ) including recent work reported by the authors concerning the effect of pressure on the solvolysis of benzyl chloride in several aqueous DMSO solvent systems (1). It was found in this study, and many others of the same type (5), that variation in solvent composition greatly influences the various psuedothermodynamic parameters of activation through differential effects on the properties of the initial and transition states. Since these properties are determined, at least in part, by the structural and molecular interaction properties of the solvent, it is necessary to possess detailed information on solvent structure and the extent of intercomponent interaction if the kinetic behavior is to be fully understood.It is generally accepted that deviation of liquid mixtures from ideality is a consequence of intercomponent interaction. Many studies, both thermodynamic and non-thermodynamic, have been performed in an effort to characterize the type and extent of these interactions in a great variety of liquid mixtures. Surprisingly, however, few studies appear to have been made on the energy-volume coefficient of binary liquid mixtures. Since both the energy-volume coefficient and the cohesive energy density are closely related to the extent and strength of intermolecular interaction, it seems that these two parameters would be of particular value in investigating the structural properties and intercomponent interactions in liquid mixtures.