Raquel M. C. Gonçalves

Enthalpies of solution oft-butyl chloride and bromide and carbon tetrachloride and tetrabromide in alcohols

Standard enthalpies of solution of t-BuX and CX4 (X=Cl and Br) in several alcohols are reported as measured by a calorimetric method. The corresponding transfer functions from the gas phase were calculated.

Calorimetric study of the solution process of tetramethylsilane in alcohols

Abstract Calorimetrically measured enthalpies of solution of tetramethylsilane into 16 alcohols, containing from 1 to 6 carbon atoms, are reported at 25°C and infinite dilution. These values are combined with the vaporization enthalpy of the solute to obtain standard enthalpies of gaseous tetramethylsilane and data are analysed in terms of the solvent structures. The solution functions for tetramethylsilane (TMS) are compared with the solution functions for tert-butyl halides (t-BuX) in order to obtain information on ert-butyl halide-alcohol interactions. For this purpose, values of solution enthalpies are also determined for tert-butyl chloride, bromide and iodide in pentan-3-ol, 2-methylbutan-2-ol and hexan-1-ol. The limitations of the use of TMS as “inert” model solute of t-BuX are discussed. However, the application of the Onsager reaction field theory is found to be useful in the analysis of the influence of the eccentricity factor on the interaction enthalpy and leads us to conclusions regarding the relative importance of dipolar solute-solvent interaction and solvent reorganization on the solution process of t-BuX in alcohols.

Linear solvation-energy relationships: solvolytic reactions of t-butyl bromide and t-butyl iodide in hydroxylic solvents

Solvent effects on the solvolytic reactions of ButBr and Butl in water, and 12 monoalcohols and 10 dialcohols, from 1 to 5 carbon atoms, have been analysed in terms of linear solvation energy relationships. The experimentally determined rate constants, at 25 °C, are well correlated through equations of the form log k=a0+a1g(η)+a2ETN+a3C where g(η) is a function of the refractive index, ETN is the normalized Dimroth and Reichardt parameter and C is the solvent cohesive pressure. The correlation analysis revealed significant information on the solvent–solvent–solute interactions. It is also shown that results are in good agreement with previous analysis using different approaches and other sets of solvents.

The enthalpies of solution of 2-chloro-2-methylpropane, 2-chloro-2-methylbutane and 3-chloro-3-methylpentane in mono- and dialcohols at 298.15 K

Abstract The enthalpies of solution at infinite dilution of 2-chloro-2-methylpropane in 9 dialcohols and of 2-chloro-2-methylbutane and 3-chloro-3-methylpentane in 19 mono- and dialcohols, at 298.15 K, were measured using a solution calorimeter. These values are discussed in terms of solute-solvent interactions. Together with previous data, this information provides a thermodynamic picture of the effect of the size of the alkyl chlorides and the structure of the alcohols.

The interaction of xenon with n-alkane solvents: Comparison between different cavity models

A recently proposed model for calculating the energetics of cavity formation in liquids is used to study the interaction of rare gases in n-alkane solvents. It is observed that the energy and the entropy of interaction of a given solute with different n-alkane solvents are very similar and show a monotonic variation with the n-alkane carbon number. This behaviour, which is not observed when other methods are used to calculate the energetics of cavity formation, reinforces the idea of the similarity of the contact energies of the different n-alkane molecules.

The cavity models and the curvature dependence of the surface tension. Spherical cavities in anisotropic solvents

In the present work the solution process of globular solutes (xenon, cyclohexane, cyclooctane and adamantane) in n-alkane solvents is analyzed. New experimental data on solution enthalpies of adamantane in those solvents are presented. The cavity model previously proposed is corrected with respect to the dependence of the surface tension on the curvature radius of the microscopic cavity and a new equation is proposed to describe this dependence.

Alcoholysis of t-butyl chloride in branched and straight-chain alcohols: a kinetic and calorimetric study

Kinetic and related calorimetric data are reported for the alcoholysis of t-butyl chloride. Heat capacities of solution and activation are used to probe the role of solvent in the activation process. Partial molar heat capacities of activation, ground, and transition states differ for reaction in normal and branched alcohols. Structural and mechanistic distinctions between the two classes of solvolytic reaction are established.

Solution enthalpies of 2-chloro-2-methylpropane in the binary alcoholic mixtures methanol—1,2-ethanediol, ethanol—1,2-ethanediol and 2-methoxyethanol—1,2-ethanediol

Abstract The enthalpies of solution at infinite dilution of 2-chloro-2-methylpropane ( t -BuCl) in methanol—1,2-ethanediol, ethanol—1,2-ethanediol and 2-methoxyethanol—1,2-ethanediol solvent mixtures were measured at 298 K using a calorimetric technique. These values were determined for nine different mole fractions of the alcoholic mixtures. The preferential solvating abilities of the various solvents towards t -BuCl are compared and analysed in terms of the molecular structures of the alcohols.

QUANTITATIVE FORMULATION OF REACTIVITY IN TERMS OF SOLVENT AND SUBSTRATE PROPERTIES. SOLVOLYSIS OF TERT-BUTYL HALIDES IN HYDROXYLIC SOLVENTS

Experimental rate constant values for the solvolysis of tert-butyl chloride in 12 alcohols at 25 °C are presented. These results, together with previous data, are well correlated through the linear solvation energy relationship log k=a0+a1 g(η)+a2ENT+a3C where g(η) is a function of the refractive index, ENT is the normalized Dimroth and Reichardt parameter and C is the solvent cohesive energy density. The same is true for tert-butyl bromide and iodide.A statistical treatment relating the experimental values of the solvolytic rate constants of the three halides in the same set of hydroxylic solvents (water, 8 monoalcohols and 10 dialcohols) to the properties of the solvents [g(η), ENT and C] and of the substrate [molar volume (V) and dipole moment (µ)] simultaneously was performed.

Kinetics and activation thermodynamics of the solvolysis of tert-pentyl and tert-hexyl halides in alcohols

The influences of solvent and substrate were interpreted through the values of rate constants and infinite dilution activity coefficients obtained for the solutes 2-chloro- and 2-bromo-2-methylbutane and 3-chloro-3-methylpentane in several monohydric alcohols at 298.15 K.