Octahedral cobalt(III) complexes in dipolar aprotic solvents. XIII. The isomerization of cis- and trans-Dibromobis(ethylenediamine)cobalt(III) ions, [CoBr2 em2]+, in anhydrous sulpholane

1968 ◽  
Vol 21 (3) ◽  
pp. 595 ◽  
Author(s):  
WR Fitzgerald ◽  
DW Watts
Keyword(s):  
Equilibrium Constants ◽  
Activation Parameters ◽  
Ion Pair ◽  
Pair Formation ◽  
Isomerization Reaction ◽  
State Entropy ◽  
Enthalpy Changes ◽  
Solvent Molecules ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The isomerization of cis- and trans-[CoBr2 en2]+ has been studied in anhydrous sulpholane (tetramethylene sulphone). No evidence has been found for the presence of species containing coordinated solvent molecules, and the mechanism of isomerization of both isomers is interpreted as SNl the rates being influenced by ion-pair formation. Activation parameters have been measured for the isomerization of both species at various bromide concentrations. Equilibrium constants and standard state entropy and enthalpy changes for the isomerization reaction and for the formation of the cis-[CoBr2 en2]+ .......Br- ion pair have been measured.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. II. Association between cis- and trans-dichlorobisethylenediamine cobalt(III) cations,[Co en2 Cl2]+, and chloride and bromide ions in the solvents NN-dimethylformamide, dimethyl sulphoxide, and LVN-dimethylacetamide

1966 ◽  
Vol 19 (1) ◽  
pp. 43 ◽  
Author(s):  
WA Millen ◽  
DW Watts
Keyword(s):  
Spectrophotometric Method ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Dimethyl Sulphoxide ◽  
Aprotic Solvents ◽  
Ion Association Constants ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

Ion association constants at 30� have been determined for the cis-[Co en, Cl2]+Cl- ion pair in NN-dimethylformamide (DMF), NN-dimethylacetamide (DMA), and at 20.0�, 25.0�, and 30.0� in dimethyl sulphoxide (DMSO), by a spectrophotometric method. Association constants for the cis-[Co en2 Cl2]+Br- and the trans- [Co en2 Cl2]+Cl- ion pairs have also been determined in DMF at 30�.

Octahedral chromium(III) complexes in dipolar aprotic solvents. I. The isomerization of cis- and trans-Dichlorobisethylenediamine-chromium (III) ions in anhydrous NN-dimethylformamide

1967 ◽  
Vol 20 (1) ◽  
pp. 53 ◽  
Author(s):  
DA Palmer ◽  
DW Watts
Keyword(s):  
Activation Parameters ◽  
Chloride Ion ◽  
Kinetics And Mechanism ◽  
Significant Part ◽  
Aprotic Solvents ◽  
Free Chloride ◽  
System Activation ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The kinetics and mechanism of the isomerization of cis- and trans- dichloro- bisethylenediaminechromium(III) ions, cis- and trans-[CrCl2 en2]+, have been investigated in anhydrous NN-dimethylformamide (DNF). The complex cis- chlorodimethylformamidebisethylenediaminechromium- (III), cis-[CrCl(DMF) en2]2+, is found to be a necessary intermediate and to remain a significant part of the system at equilibrium. The equilibria are found to depend on the concentration of free chloride ion as has been found in the comparable cobalt system.��� Activation parameters have been determined for isomerization reactions using both the cis- and trans-(CrCl2 en2)+ ions as starting materials and for the chloride entry reaction into the cis-[CrCl(DMF) en2]2+ ion which has been isolated as cis-[CrCl(DMF) en2](ClO4)2,R2O.

Solute–solvent interactions in the association of hexacyanoferrate(III) with group II A cations. A calorimetric study

1982 ◽  
Vol 60 (14) ◽  
pp. 1828-1831 ◽  
Author(s):  
Roberto Aruga
Keyword(s):  
Equilibrium Constants ◽  
Ion Pairs ◽  
Ion Pair ◽  
Pair Formation ◽  
Calorimetric Study ◽  
Thermodynamic Quantities ◽  
Gibbs Function ◽  
Direct Calorimetry ◽  
Solvent Interactions ◽  
Enthalpy Of Association

Enthalpy of association of hexacyanoferrate(III) ion with Mg(II), Ca(II), Sr(II), and Ba(II) cations has been determined by direct calorimetry. Using the equilibrium constants, Gibbs function and entropy were also obtained. Measurements were carried out in aqueous medium at 25 °C and ionic strength I = 0.1 mol L−1. Examination of the thermodynamic quantities obtained and calculation of the distance of closest approach between cation and anion show the presence of different desolvation processes for the metals studied. More particularly, solvent-separated ion pairs in the case of magnesium and contact pairs in the case of barium seem to be present. The presence of desolvation processes is uncertain for calcium and strontium. The ΔH0 and ΔS0 values show also an important influence from solvent-destructuring processes on ion pair formation.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. XI. Anation of cis-chlorodimethylformamidebisethylenediaminecobalt(III) by bromide ion, and solvolysis and isomerization of cis-and trans-bromochlorobisethylenediaminecobalt(III) ions in anhydrous N,N-dimethylformamide

1967 ◽  
Vol 20 (12) ◽  
pp. 2623 ◽  
Author(s):  
IR Lantzke ◽  
DW Watts
Keyword(s):  
Activation Parameters ◽  
Ion Association ◽  
Aprotic Solvents ◽  
Bromide Ion ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The anation of the cis-chlorodimethylformamidebisethylenediaminecobalt(III) ion (cis- [CoCl(DMF) en2]2+) by bromide ion in N,N-dimethylformamide (DMF) has been studied. The reaction has an SNIIP1 mechanism, and when due allowance is made for ion association its activation parameters closely parallel those of other SNIIP anation reactions in DMF. The solvolysis and isomerization of the dichlorobisethylenediaminecobalt(III) ions (cis- and trans-[CoCl2 en2]+) and the bromochlorobisethylenediaminecobalt(III) ions (cis- and trans- CoBrCl en2]+) in DMF have been examined over a range of anion concentration. In all cases solvolysis reactions are important, although direct isomerization appears to become an important path for the reaction of the trans complexes at high anion concentrations. Solvolysis of the cis-[CoCl2 en2]+ ion involves an SN2 mechanism.1 The cis-[CoBrClen2]+, trans-[CoCl2 en2]+, and trans-[CoBrCl en2]+ ions all react by an SN1 mechanism.

Octahedral cobalt(III) complexes in dipolar aprotic solvents. IV. Solvolysis and isomerization of dibromobisethylenediaminecobalt(III) ions inanhydrous NN-dimethylformamide and NN-dimethylacetamide

1966 ◽  
Vol 19 (6) ◽  
pp. 935 ◽  
Author(s):  
WR Fitzgerald ◽  
DW Watts
Keyword(s):  
Concentration Dependence ◽  
Ion Association ◽  
Ion Pair ◽  
Aprotic Solvents ◽  
Equilibrium System ◽  
Lower Stability ◽  
Bromide Ion ◽  
Cis And Trans ◽  
Dipolar Aprotic Solvents

The equilibrium system (SOL)+Br-+cis-[CoBr2 em]+ = cis-[CoBr(SOL) en2]2++2Br-   =trans[CoBr2en2]2++Br-+SOL where SOL represents either of the solvents NN-dimethylformamide (DMF) or NN-dimethylacetamide (DMA), has been studied. The compounds cis- [CoBr(DMF) en2](ClO4)2, and cis-[CoBr(DMA) en2]XO3,ClO4, have been isolated and thus it has been possible to study these equilibria using as starting materials both the cis- and trans-dibromo complexes (cis- and trans-[CoBr2 en2]+) and the solvento complexes (cis-[CoBr(DXA) en2]2+ and cis-[CoBr(DMF) en2]2+). The mechanism of the bromide entry reactions cis-[CoBr(SOL) en2]2+ +Br- = cis- and trans-[CoBr2 en2]++SOL is bimolecular in DMA while in DMF the reaction is dissociative: the rate showing bromide concentration dependence only in the concentration range where ion association is not complete. In both systems the isomerization proceeds mainly through the solvento complex; in dimethylacetamide there is evidence for a seven-coordinated intermediate. The isomerization equilibria are found to be bromide concentration dependent, cis-[CoBr2 en2]+ being favoured by high bromide concentrations. This is consistent with the lower stability of the trans-[CoBr2 en2]- ion pair with bromide ion.

Solvation of ions. XIX. Thermodynamic properties for transfer of single ions between protic and dipolar aprotic solvents

1974 ◽  
Vol 27 (3) ◽  
pp. 477 ◽  
Author(s):  
BG Cox ◽  
GR Hedwig ◽  
AJ Parker ◽  
DW Watts
Keyword(s):  
Thermodynamic Properties ◽  
Water Structure ◽  
Dimethyl Formamide ◽  
Aprotic Solvents ◽  
Free Energies ◽  
Enthalpy Changes ◽  
Solvation Of Ions ◽  
Anions And Cations ◽  
Solvent Molecules ◽  
Dipolar Aprotic Solvents

Standard molar free energies, enthalpies and entropies of transfer of some uni-univalent electrolytes from water to methanol, N-methylformamide, formamide, dimethyl sulphoxide, N,N-dimethyl- formamide, propylene carbonate, sulpholane, N-methylpyrrolidone and acetonitrile are presented. They have been divided into the corresponding thermodynamic properties for single ions by means of extrathermodynamic assumptions. Changes in the chemistry of anions on transfer from protic to dipolar aprotic solvents are mainly a function of enthalpy changes. There is a substantial loss of entropy on transferring both anions and cations from water to non-aqueous solvents. Entropies of transfer can be interpreted in terms of ordering and disordering solvent molecules and a uniquely extensive water structure. Evidence for solvation of the first and second kind in water is presented. Enthalpies of transfer from water are exothermic for cations but endothermic for many anions.

Mutarotation of D(+)-glucose. III. Evidence for cooperative and competitive nucleophilic catalysis by molybdenum(VI) and tungsten(VI) anions

1984 ◽  
Vol 37 (7) ◽  
pp. 1411 ◽  
Author(s):  
CJ O'Conner ◽  
AAT Bailey
Keyword(s):  
Activation Parameters ◽  
Ion Pair ◽  
Pair Formation ◽  
Base Catalysis ◽  
Nucleophilic Catalysis ◽  
General Base ◽  
Rate Determining Step ◽  
Conjugate Acid ◽  
Oxo Anions ◽  
Charged Ions

The rate of mutarotation of α-D(+)-glucose is subject to general base catalysis by a variety of oxo anions. The relative magnitudes of the second-order rate constants are B4O72->W7O246->Mo7O246- > HCO3->WO42->MoO42- Catalysis by W7O246- and Mo7O246- is competitive but that by WO42- and MoO42- is cooperative. A mechanism for catalysis by the polymeric anions is proposed which involves ion-pair formation between the anion and the conjugate acid of glucose. Specifically oriented aquation sheaths about the charged ions cause them to act as enhanced nucleophiles in the rate-determining step to form the aldehyde intermediate. Activation parameters support this model.

Reply to the ‘Comment on “The size and structure of selected hydrated ions and implications for ion channel selectivity”’ by A. Zavitsas, RSC Adv., 2016, 6, 92771

RSC Advances ◽  
2016 ◽  
Vol 6 (95) ◽  
pp. 93217-93218 ◽  
Author(s):  
Zhong-Hua Yang
Keyword(s):  
Aqueous Solution ◽  
Ion Channel ◽  
Experimental Evidence ◽  
Equilibrium Constants ◽  
Ion Pair ◽  
Pair Formation ◽  
Hydrated Ions ◽  
Channel Selectivity ◽  
Ion Channel Selectivity ◽  
Size And Structure

We believe that in Zavitsas' previous work the assumption of “ideality” on an aqueous solution of an electrolyte conflicts with experimental evidence and the calculation of ion-pair formation equilibrium constants to demonstrate the existence of an ion-pair is artificial.

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