Binary Aqueous Solvent Mixtures Research Articles

Catalytic cyclophanes VII. Esterase activity of a bisimidazolyl‐cyclophane

AbstractWe report the synthesis of the novel tetraoxa[6.1.6.1]paracyclophane 3 with two imidazole residues attached to the benzene rings of one of the two diphenylmethane spacers that shape the macrocyclic cavity. Four acetic acid residues diverge from the central carbon atoms of the two spacer units and ensure solubility of 3 in water and binary aqueous solvent mixtures. Cyclophane 3 forms stoichiometric inclusion complexes with nitronaphthyl acetates in aqueous phosphate buffers (pH 8) and catalyzes the hydrolysis of bound substrates under turnover conditions.

Solubilities and solvation of β-diketonate complexes

Solubilities are reported for the acetylacetonates Cr(acac) 3, Fe(acac) 3, Co(acac) 3, Co(acac) 2, Ni(acac) 2, Cu(acac) 2, V(acac) 2 and UO 2(acac) 2 in binary aqueous solvent mixtures with co-solvents including methanol, isopropanol, t-butyl alcohol, dioxan and dimethyl sulphoxide. Solubilities of the bis-trifluoroacetylacetonate, bis-hexafluoro-acetylacetonate and bis-dibenzoylmethane complexes, UO 2(ligand) 2, in methanol-water are also reported. Trends of transfer chemical potentials derived from these solubilities are discussed in terms of solvation and preferential solvation by water and the organic (co)solvents.

Solvation and reactivity of tris(diimine)–iron(II) complexes in aqueous ethane-1,2-diol, propane-1,2,3-triol and sucrose

The dependence of rate constants for base hydrolysis on solvent composition for several iron(II)–diimine complexes has been established for aqueous ethane-1,2-diol (ethylene glycol) and aqueous propane-1,2,3-triol (glycerol) mixtures, and for aqueous sucrose solutions. These dependences are compared with analogous reactivity trends for binary aqueous solvent mixtures containing monohydroxylic alcohols. Transfer chemical potentials for iron(II)–diimine complexes, and for simple cations and anions, have been estimated on the TATB assumption for transfer to aqueous ethane-1,2-diol and aqueous propane-1,2,3-triol. These transfer chemical potentials allow resolution of the observed reactivity trends into initial-state and transition-state contributions for the aqueous ethane-1,2-diol mixtures. Such information on the role of solvation in this type of reaction is complented by the determination of activation volumes for base hydrolysis for four iron(II)–diimine complexes in aqueous ethane-1,2-diol.

Kinetics of oxidation of iodide by hexacyanoferrate(II) in binary aqueous solvent mixtures

The kinetics of the oxidation of iodide by hexacyanoferrate(III) have been studied in different H2O-methanol, t-butanol, ethylene glycol glycerol, glucose or sucrose mixtures. Specific solvent effects are found as shown by the different trends in activation parameters and in the variations of the initial state and transition state chemical potentials as observed in different media. From the results of a multiple linear correlation, it is concluded that the kinetics are controlled by the ionizing power of the solvents, their relaxation times and the outer sphere reorganization energies.

Solvent effects in molecular recognition

Abstract

Solvatochromic hydrogen bond donor acidity of aqueous binary solvent mixtures for reversed-phase liquid

Solvatochromic hydrogen bond (HB) donor acidity (α m) values for aqueous mixtures of methanol, ethanol, isopropanol, acetonitrile and tetrahydrofuran were measured by electronic absorption spectroscopy employing bis[α-(2-pyridyl)-benzylidine-3,4-dimethylaniline]bis(cyano)iron(II) as an indicator, and compared to available literature values. The HB donor acidity of all the aqueous organic mixtures increases in a nonlinear fashion as water is added to the organic solvent. For mixtures of acetonitrile and tetrahydrofuran, which are not acidic or are only slightly acidic, with water α m increases rapidly as a small amount of water is first added, then shows a plateau region, and finally slowly rises to the acidity value of water. In contrast, the α m for the mixtures of methanol, ethanol and isopropanol, which are quite acidic, increase slowly as the first small amount of water is added and then increase rapidly as the mixtures approaches pure water. Literature values of α m for water-methanol mixtures, which were determined from the D T(30) values of Reichardt's betaine dye, showed a minimum in the plot of α m vs. volume fraction of organic component. It was also shown that the solvophobicity parameter ( S p) of methanol- and ethanol-water mixtures can be described by a combination of the dipolarity (π m *) and HB donor acidity (α m) of the mixtures.

Solvation and reactivity of inorganic complexes: F vs. H and CF3vs. CH3

We are currently examining the effects of the replacement of H by F, and of CH3 by CF3, in the ligands of selected inorganic complexes on solvation and on reactivity. We are also comparing CF3CH2OH with CH3CH2OH, and CF3CH(OH)CF3 as solvents for inorganic complexes.Solute-solvent interactions are being probed through transfer chemical potentials and through solvatochromism. We shall compare transfer chemical potential trends for complexes M(acac)3, M(tfac)3, and M(hfac)3, and for some iron (II) complexes of diimine ligands and their fluoro-analogues, in binary aqueous solvent mixtures. The trends which are emerging show that replacement of H by F results in a significant increase in hydrophilicity, with the determined transfer chemical potentials giving a quantitative measure of differences. The solvatochromic properties of ternary iron(II)-diimine-cyanide give an alternative means of comparing solute-solvent interactions, both in relation to fluorine substitution in the diimine ligands and in respect of the solvating properties of the fluoroalcohols mentioned above.Replacement of H by F, or of CH3 by CF3, in iron(II) complexes of Schiff bases derived from appropriate results in much faster rate constants for base hydrolysis. It is hoped to present an initial state-transition state analysis of reactivity trends in methanol-water mixtures in order to establish precisely how solvation changes affect reactivities in this type of reaction.

Cobalt(III)-salicaldehyde-aminophenol complexes: solubilities, transfer chemical potentials and solvation in binary aqueous solvent mixtures

Solubilities are reported for four cobalt(III) complexes of Schiff bases derived from 2-aminophenol and (substituted) salicaldehydes, in aqueous methanol, and for one of these complexes also in aqueous t-butyl alcohol and in aqueous acetone. The derived trends of transfer chemical potentials with solvent composition are discussed in relation to the nature of the ligand and the nature of the co-solvent. Solvation characteristics for the title complexes are compared with those of other inorganic complexes, particularly of cobalt(III).

Preferential solvation of the europium(III) ion in water–non-aqueous solvent mixtures. A luminescence lifetime study

For binary aqueous solvent mixtures the solvent composition in the first solvation sphere of Eu3+ has been determined at 25 °C by measuring the luminescence lifetime. In the systems water–acetone, water–acetonitrile and water–1,4-dioxane the first solvation sphere of Eu3+ is exclusively occupied by water molecules even at bulk-phase mole fractions of water as low as 0.1. Eu3+ is preferentially solvated by water in water–methanol and by DMSO in water–DMSO mixtures over the whole range of solvent composition. In water–DMF mixtures Eu3+ is preferentially solvated by DMF when the mole fraction of DMF is below 0.7 and by water when it is above that value. In all the systems the degree of preferential solvation varies considerably with solvent composition. These results for the preferential solvation of Eu3+ are compared with those of Al3+ and of alkali-metal ions obtained by the n.m.r. method.

Effect of Amines on the Kinetics of alkaline Decomposition of Benzyltriphenylphosphonium Chloride in Binary Solvent Mixtures

AbstractThe kinetics of decomposition of benzyltriphenylphosphonium chloride by sodium hydroxide was studied in binary aqueous solvent mixtures ranging from pure water to about 70% (v/v) of dipolar aprotic solvents such as DMSO or acetone in presence of a series of aliphatic and aromatic amines. The rate, which is directly proportional to the organic solvent content, was found to increase to a maximum at 0.1 M amine concentration and then to decrease. The small increase in rate due to the addition of amine is explained on the basis of an amine‐water interaction, where the concentration of OH− ions in the solution increases slightly due to the ability of the amines to abstract protons from water molecules in the medium. However, the decrease in rate beyond 0.1 M amine concentration is explained as due to the decrease of hydroxide ion concentration by formation of a weakly ionised quaternary ammonium hydroxide. The observed activation energies, thermodynamic parameters and radii of the activated complex for all solvent compositions are computed. The effect of the bulk dielectric constant on the reaction rate was investigated in the light of the available electrostatic theories.

Kinetic and spectroscopic intimations of intermediates in nucleophilic attack at diimine complexes of iron(II) and of molybdenum(O)

Kinetics of nucleophilic substitution at a range of low-spin iron(II)diimine complexes have been examined in the presence of a variety of salts, to probe the role of hydroxide and cyanide as nucleophiles and of other ions in ion association equilibria. Equilibrium constants for interaction of hydroxide and of cyanide with many of these ligands, free or complexed with iron(II) or molybdenum(0), have been measured, in water and in binary aqueous solvent mixtures. Effects of solvent, temperature, and pressure on rate constants and on equilibrium constants have been monitored for selected systems. In the light of these results, and of ancillary qualitative observations, we discuss the role and nature of intermediates in nucleophilic substitution reactions of transition metaldiimine complexes.

Initial state and transition state solvation effects in the oxidation of iodide and catechol by hexachloroiridate(IV) in binary aqueous solvent mixtures

Rate constants are reported for hexachloroiridate(IV) oxidation of iodide in methanol–, ethanol–, t-butyl alcohol–, ethylene glycol–, glycerol–, acetone–, acetonitrile–, and dimethyl sulphoxide – water solvent mixtures, and for the hexachloroiridate(IV) oxidation of catechol in methanol–water mixtures. With the aid of ancillary solubility data and measurements, solvent effects on reactivity have been analysed into initial state and transition state components. In the latter, there are probably both electron transfer and diffusion contributions since it is not possible to identify uniquely the separate kinetic steps associated with the activation process. In these redox systems, however, transition state solvation changes dominate. This conclusion is compared with initial state – transition state effects in the reaction of catechol with hexahydroxoantimonic acid, in the bromate oxidation of bromide, the peroxodisulphate oxidation of iodide, and with patterns established earlier for substitution at inorganic centres. In view of some disagreements and uncertainties in the literature concerning the number of molecules of water of crystallisation in potassium hexachloroiridate(III) and hexachloroiridate(IV), this matter, of considerable importance to hexachloroiridate transfer parameter estimation, is briefly reviewed.

ChemInform Abstract: Enthalpies of Solution of Lanthanum, Gadolinium and Ytterbium Trichlorides in Binary Aqueous Solvent Mixtures.

Chemischer InformationsdienstVolume 13, Issue 24 Physical Inorganic Chemistry ChemInform Abstract: Enthalpies of Solution of Lanthanum, Gadolinium and Ytterbium Trichlorides in Binary Aqueous Solvent Mixtures. M. J. BLANDAMER, Search for more papers by this authorJ. BURGESS, Search for more papers by this authorJ. KIJOWSKI, Search for more papers by this author M. J. BLANDAMER, Search for more papers by this authorJ. BURGESS, Search for more papers by this authorJ. KIJOWSKI, Search for more papers by this author First published: June 15, 1982 https://doi.org/10.1002/chin.198224020Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume13, Issue24June 15, 1982 RelatedInformation

Initial state and transition state solvation effects in the cobaltitungstate oxidation of iodide in binary aqueous solvent mixtures

Rate constants are reported for 12-tungstocobaltate(III) [CoW12O40]5− oxidation of iodide in water and in binary aqueous solvent mixtures containing up to 40% methanol, 40% acetonitrile, or 60% dimethyl sulphoxide. From these kinetic results, solubility measurements on potassium 12-tungstocobaltate(III), and published data on Gibbs free energies of transfer of appropriate ions, it has been deduced that the dominant factor in determining the marked decrease in rate observed on going from water into the binary aqueous solvent mixtures is destabilisation of the transition state for the electron-transfer reaction.

Enthalpies of solution of lanthanum, gadolinium and ytterbium trichlorides in binary aqueous solvent mixtures

Enthalpies of solution are reported for anhydrous lanthanum trichloride in methanol-, ethanol-, t-butyl alcohol-, and dimethyl sulphoxidewater mixtures, for anhydrous gadolinium trichloride in methanolwater mixtures, and for ytterbium trichloride in methanol- and dimethyl sulphoxidewater mixtures, at 298.2 K. The estimation of enthalpies of transfer of lanthanide(III) cations into these binary aqueous solvent mixtures is discussed.

Intermediates in reactions of the diimine complex trisferrozineiron(II) with hydroxide or cyanide in binary aqueous solvent mixtures and in micelles

Kinetic and spectroscopic observations are reported for the reaction of tris-ferrozineiron(II) with hydroxide in DMSO- and DMF-H2O mixtures and with cyanide in MeOH- and DMSO-H2O mixtures. Micellar effects (CTAB) are described for the reactions of tris-ferrozineiron(II) and of tris-5-sulphonato-1,-10-phenanthrolineiron(II) with hydroxide. Results for the ferrozine complex are discussed in terms of mechanisms involving intermediates formed by attack of hydroxide or cyanide at the coordinated ligand.

ChemInform Abstract: INITIAL‐STATE AND TRANSITION‐STATE CONTRIBUTIONS TO SOLVENT EFFECTS ON REACTIVITY FOR THE REACTION OF CIS‐DICHLOROBIS(4‐CYANOPYRIDINE)PLATINUM(II) WITH THIOUREA IN BINARY AQUEOUS SOLVENT MIXTURES

Chemischer InformationsdienstVolume 11, Issue 5 Organoelement Compounds ChemInform Abstract: INITIAL-STATE AND TRANSITION-STATE CONTRIBUTIONS TO SOLVENT EFFECTS ON REACTIVITY FOR THE REACTION OF CIS-DICHLOROBIS(4-CYANOPYRIDINE)PLATINUM(II) WITH THIOUREA IN BINARY AQUEOUS SOLVENT MIXTURES M. J. BLANDAMER, M. J. BLANDAMERSearch for more papers by this authorJ. BURGESS, J. BURGESSSearch for more papers by this authorS. J. HAMSHERE, S. J. HAMSHERESearch for more papers by this author M. J. BLANDAMER, M. J. BLANDAMERSearch for more papers by this authorJ. BURGESS, J. BURGESSSearch for more papers by this authorS. J. HAMSHERE, S. J. HAMSHERESearch for more papers by this author First published: February 5, 1980 https://doi.org/10.1002/chin.198005339Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue5February 5, 1980 RelatedInformation

Solubility of potassium cyanide in mixed aqueous and non-aqueous media; Gibbs free energies of transfer of the cyanide ion

Solubilities of potassium cyanide in a variety of non-aqueous solvents and binary aqueous solvent mixtures are reported. From these results and from published data on Gibbs free energies of transfer of the potassium ion, Gibbs free energies have been estimated for transfer of the cyanide ion from water into a selection of mixed aqueous and non-aqueous media. With the aid of these transfer parameters, reactivity trends for the reaction of the [Fe(bipy)3]2+ cation (bipy = 2,2′-bipyridyl) with cyanide ion in mixed aqueous solvents are analysed for initial-state and transition-state contributions.

Initial state and transition state effects in the mercury(II)-catalysed aquation of chlorotransition-metal complexes in binary aqueous solvent mixtures

Rate constants are reported for the mercury(II)-catalysed equation of the [Co(NH3)5Cl]2+, trans-[Co(en)2Cl2]+, and [ReCl6]2– ions in water-rich methanol–, ethanol–, butyl alcohol–, ethylene glycol–, glycerol–, dioxan–, and acetonitrile–water mixtures. The observed reactivity trends are discussed and, as far as possible, analysed into initial- and transition-state components from estimated single-ion Gibbs free energies of transfer. In connection with this analysis the solubilities of the tetraphenylborates of mercury(II) and of caesium in several binary aqueous solvent mixutres are also reported.

Substitution of azide atNNN?N?-tetraethyldiethylenetriaminechlorogold-(III) in binary aqueous solvent mixtures

Rate constants are reported and discussed for the reaction of [Au(Et4dien)Cl]2+ with HN3 (pH = 1) and of [Au(Et4dien-H)Cl]+ with N3− (pH = 7) in several binary aqueous solvent mixtures.