Michael J. Blandamer

Isentropic compressibilities : Experimental origin and the quest for their rigorous estimation in thermodynamically ideal liquid mixtures

In this review, attention is initially focused upon the evolution of the Newton-Laplace Equation, that links the measured speed of sound in a fluid in conjunction with its density, to a reliable estimate of its isentropic compressibility κS. Definitions of ideal and excess isentropic quantities are formulated on the premise that the thermodynamic properties of an ideal mixture are mutually related in the same manner as are those of a real mixture or a pure substance. It is shown that both intensive and extensive properties can be derived from the ideal Gibbs energy. Different approaches previously used to calculate ideal isentropic quantities are examined and some subtle errors are identified. The consequences of using conflicting definitions are pointed out. Isentropic pressure derivatives obtained under different conditions and empirical models for estimating the differences between ultrasonic speeds in real and ideal liquid mixtures are discussed.

Initial state and transition state solvation in inorganic reactions

A. Introduction _ _ _ _ . . _ _ _ . _ _ _ _ _ _ . _ . _ . _ . 93 B. Principfes of the analysis . _ _ . . . _ _ . . . . _ * 97 C. Reactions involving neutral reactants . . . _ . . . _ _ 99 D. Single ion properties. . . . _ . _ . _ _ _ _ . _ . _ . . . _ . 104 E. Substitution reactions . . . . . . . . . . . . . . . . . . . 106 (i) Aquation of chloro-cobalt(II1) complexes _ _ . _ . . . . . . . _ 106 (ii) Tris-( 2,2’-bipyridyl)iron( II) plus either cyanide or hydroside ions . . _ . 109 F. Metal ion catalysed reactions _ . _ . . . _ + _ . . . . . . * 112 (i) Mercury(I1) cataiysed aquation _ _ _ _ _ _ _ _ _ _ _ . . _ _ . 112 (ii) Other reactions . . . . _ . . . _ _ . . . . . . . _ 112 G. Redox reactions _ _ . . _ _ _ . . _ . _ . _ . . . . . . -. 113 (i) General . . . . . _ . . . . . . . . . . . . . . . . . 113 (ii) Hexachloroiridate( IV) oxidations . . . . _ . . . . . . . . . . 113 (iii) Peroxodisulphate oxidations _ . . . . . . . . . . . _ . . . 114 H. Transition state models _ _ _ _ _ . . _ _ . . . . _ . . . * . _ 115 I. Two stage reactions . _ _ _ _ _ _ _ _ _ _ . _ . . . _ * * . 115 J. Conclusions and discussion . . _ . . . . . . . . . . . . . _ . 116 References . _ . . _ . _ . . . . . . , _ . . . . . . . . . 119

Apparent molar isentropic compressions and expansionsof solutions

Isentropic compressibilities of solutions κS are readily calculated using the Newton–Laplace equation together with measured speeds of sound and densities. The result is an apparent molar isentropic compression for a given solute-j, ϕ(KSj; def) and a limiting property, ϕ(KSj; def)∞. This review examines the definition and calculation of ϕ(KSj; def) and ϕ(KSj; def)∞, commenting on the related isentropic expansions, ϕ(ESj; def) and ϕ(ESj; def)∞. We describe the thermodynamics which underpins the use of isentropic properties in the study of solute–solvent and solute–solute interactions.

Thermodynamics of Micellar Systems: Comparison of Mass Action and Phase Equilibrium Models for the Calculation of Standard Gibbs Energies of Micelle Formation

Micellar colloids are distinguished from other colloids by their association-dissociation equilibrium in solution between monomers, counter-ions and micelles. According to classical thermodynamics, the standard Gibbs energy of formation of micelles at fixed temperature and pressure can be related to the critical micelle concentration. This relation is different for two models which are widely used to describe micelle formation, namely the Phase Separation and the Mass Action Models. These approaches and the assumptions upon which they are based are analysed in this paper. We show that the two models can be generalised to include surfactant salts having different stoichiometries.

The concepts of non-Gibbsian and non-Lewisian properties in chemical thermodynamics

The concepts of Gibbsian and non-Gibbsian, Lewisian and non-Lewisian thermodynamic variables are explored with respect to the thermodynamic properties of liquid mixtures and solutions. The general structures of equations for isochoric heat capacities, isentropic compressions and isentropic expansions are compared and contrasted. A simple rule is proposed for transcribing non-Gibbsian equations in terms of non-Lewisian partial molar properties. The bases of equations for partial molar isochoric heat capacities, isentropic compressions and isentropic expansions are examined for (i) components of liquid mixtures, and (ii) solute and solvent in solutions together with the properties of solutes at infinite dilution.

Solubilities of salts and kinetics of reaction between hydroxide ions and iron(II)–di-imine complexes in water–methanol mixtures. Derivation of single-ion transfer chemical potentials and their application to analysis of solvent effects on kinetic parameters

Kinetic data are reported for the reaction at 298 K and ambient pressure between two iron(II)–di-imine complex cations and hydroxide ions in water–methanol mixtures. Solubility data are reported for a range of inorganic salts containing simple and complex ions. Methods for calculating transfer chemical potentials of single ions are examined and, depending on the extrathermodynamic assumption, shown to predict different trends in the properties of ions in these aqueous mixtures. Further, calculated initial- and transition-state solvation effects on the kinetics are different: in some cases dramatically so. The solvation characteristics are compared for various ions in methanol–water mixtures as calculated using the tetraphenylphosphonium tetraphenylborate (TPTB) assumption, which sets the transfer chemical potential of tetraphenylphosphonium ions equal to that of tetraphenyl-boronate ions. Arguments are advanced for adopting single-ion transfer chemical potentials based on this assumption. Relationships are examined between the transfer parameters for H+, H3O+, ROH+2 and H9O+4 ions in binary aqueous mixtures, ROH + H2O.

Solvation of transition metal complexes: thermochemical approaches

Conclusion and extensionsWe hope that this Review has made readers more aware of solvation of inorganic complexes, and of the importance of such knowledge in understanding their chemistryperhaps particularly their reactivity. The approach just set out for inorganic complexes should be of considerable value in the field or organometallic chemistry. In particular, informed use of solvation characteristics should help in optimising conditions for organometallic reactions and in homogeneous catalysis. Unfortunately, solvation data on reactants are too sparse (the subject index ofComprehensive Organometallic Chemistry contains justthree entries under “solubility”!) for serious examination of reactivity trends in terms of initial state and transition state contributions to be possible in almost all areas. Moreover, there are some fundamental problems over transfer parameters. Thus, a favourite electrochemical assumption is that the ferrocene/ferrocinium redox potential is independent of solvent. Yet, the dependence of rate constants on medium for outer-sphere electron transfer in the ferrocene/ferrocinium system can only be understood(66) in terms of specific solvation effects which are incompatible with the parallel solvation changes of these two substrates implicit in the redox potential assumption. The solvation of organometallic species should prove a most rewarding area for continued study, but it will be some time before the overall picture becomes as clear as in the more limited area of classical transition metal complexes considered in the present Review.

DIFFERENTIAL SCANNING MICROCALORIMETRIC STUDY OF VESICLES IN AQUEOUS-SOLUTIONS FORMED BY DIMETHYLDIOCTADECYLAMMONIUM BROMIDE

Differential scanning microcalorimetric data for dimethyldioctadecylammonium bromide (DOAB) in dilute aqueous solutions prepared using different protocols including an ethanol injection method are compared. Reproducible data are obtained for solutions prepared using a hot-water method. Scans for very dilute solutions show evidence for processes controlled by both inter- and intra-vesicular interactions. An extremum in the scans near 47 °C is assigned to a gel to liquid crystal transition involving local domains within each vesicle comprising ca. 130 DOAB monomers.

An inverse Kirkwood–Buff treatment of the thermodynamic properties of DMSO–water mixtures and cyanomethane–water binary liquid mixtures at 298.2 K

The dependence on mole fraction of GEm for DMSO(2)–water(1) mixtures has been analysed using the Redlich–Kister equation. Derived parameters and other properties of this system have been used to calculate Kirkwood–Buff integral functions G11, G22 and G12 which are related to spatial correlation functions for the liquid mixture. Trends in these parameters as a function of mole fraction composition point to the importance of the function G12 consistent with strong intercomponent hydrogen bonding. The dependence of GEm on x2 for water(1)—cyanomethane(2) mixtures is analysed using both Redlich–Kister and orthogonal polynomial functions. At 298.2 K and ambient pressure GEm > RT/2 for x2≈ 0.4 which, for a quadratic mixture, signals partial miscibility. This complexity impinges on the analysis which requires the second differential d2GEm/dx22. Parameters derived from the dependence of GEm on x2 using orthogonal polynomials are combined with other properties of this mixture to yield the Kirkwood–Buff integral functions. In contrast to DMSO–water mixtures, the dominant terms, G11 and G22, confirm the microheterogeneity of cyanomethane–water mixtures, where x2≈ 0.3.

Kinetics of Organic Reactions in Water and Aqueous Mixtures

Publisher Summary This chapter reviews some kinetic results of aqueous systems and describes how information concerning the properties of these systems can be used in the analysis of kinetic data. The chapter also outlines some important aspects of aqueous chemistry. The phenomenon of hydrogen bonding is of paramount importance to aqueous solutions, and has seen remarkable progress although important problems remain where more than two water molecules are involved. The X-ray scattering, spectroscopic, and thermodynamic properties confirm that, in water a large proportion of the molecules are hydrogen bonded together in an open, lowdensity arrangement. The properties that determine the standard state properties of solutes in solution, for example partial molar volume and partial molar heat capacity, are examined in the chapter. These are determined by the intrinsic properties of the solute and by the solute–water interactions. The hydration characteristics of a solute are determined by a number of factors (1) the electrical properties (2) the number of hydrogen bonding sites on the solute, (3) the size of any apolar residue, (4) the degree of unsaturation or aromaticity of the hydrocarbon part of the molecule, and (5) the relative positions of polar groups in the solute, together with their freedom to rotate and their conformation. The chapter describes molecular models for aqueous solutions, which can be extended to simple monofunctional solutes, such as monohydric alcohols with large apolar groups. It also reviews the salt solutions by examining ionic hydration, and examines the properties of real solutions from the standpoint of ion–ion interactions.