Association constants for ion pairs

1986 ◽  
Vol 15 (3) ◽  
pp. 231-235 ◽  
Author(s):  
Raymond M. Fuoss
Keyword(s):  
Ion Pairs ◽  
Association Constants

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�.

scholarly journals When spectroscopy fails: The measurement of ion pairing

2006 ◽  
Vol 78 (8) ◽  
pp. 1571-1586 ◽  
Author(s):  
Glenn Hefter
Keyword(s):  
Metal Ion ◽  
Chemical Speciation ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Spectroscopic Techniques ◽  
Association Equilibria ◽  
Solvent Molecules ◽  
Contact Ion Pairs

Spectroscopic techniques such as UV/vis, NMR, and Raman are powerful tools for the investigation of chemical speciation in solution. However, it is not widely recognized that such techniques do not always provide reliable information about ion association equilibria. Specifically, spectroscopic measurements do not in general produce thermodynamically meaningful association constants for non-contact ion pairs, where the ions are separated by one or more solvent molecules. Such systems can only be properly quantified by techniques such as dielectric or ultrasonic relaxation, which can detect all ion-pair types (or equilibria), or by traditional thermodynamic methods, which detect the overall level of association. Various types of quantitative data are presented for metal ion/sulfate systems in aqueous solution that demonstrate the inadequacy of the major spectroscopic techniques for the investigation of systems that involve solvent-separated ion pairs. The implications for ion association equilibria in general are briefly discussed.

Equilibria in Acetic Acid: Ion Association Constants of Salts and the Autoprotolysis Constant of Acetic Acid at 105.7°C

1962 ◽  
Vol 15 (3) ◽  
pp. 409 ◽  
Author(s):  
RJL Martin
Keyword(s):  
Acetic Acid ◽  
Perchloric Acid ◽  
Sodium Acetate ◽  
Specific Conductivity ◽  
Ion Pairs ◽  
Sodium Perchlorate ◽  
Ion Association ◽  
Association Constants ◽  
Ion Association Constants

The ion association constants KA=[M+A-]/[M+][A-] which have been measured conductimetrically at 105 7 �C in acetic acid are : perchloric acid 0.0644 X 106, sodium perchlorate 0.1346 x 106, and sodium acetate 0.752 x 106. The parameters 6, centre to centre distance between the ions at contact, which were calculated from Bjerrum's formula, are : perchloric acid 4.52 Ǻ, sodium perchlorate 4.20 Ǻ, and sodium acetate 3.61 Ǻ. The autoprotolysis constant, K = [H2+ Ac][Ac-]= 1.17 x 10-19, was calculated from the specific conductivity of acetic acid at 105.7 �C. The acetic acidium acetate ion pairs were calculated to be 100.0% dissociated.

Stability constants for metal arsenates

2007 ◽  
Vol 4 (2) ◽  
pp. 123 ◽  
Author(s):  
Janice S. Lee ◽  
Jerome O. Nriagu
Keyword(s):  
Metal Ions ◽  
Current Knowledge ◽  
Ion Pairs ◽  
Fate And Transport ◽  
Solid Metal ◽  
Association Constants ◽  
Arsenic Acid ◽  
Arsenic Compounds ◽  
Solubility Products ◽  
Metal Arsenates

Environmental context. The behaviour of arsenic compounds is controlled by their solubility, which in turn controls both the forms and mobility of arsenic in the environment. Current knowledge on arsenic chemistry may be distorted because information available on the solubility of arsenic compounds usually does not include possible formation of metal–arsenate complexes. Our results show the formation of stable metal–arsenate complexes that have not been considered before, and this new data can be used to further examine the effect of these complexes on controlling the fate and transport of arsenic in the environment. Abstract. The formation of solid metal arsenates could conceivably reduce the concentrations of arsenate and metal ions in natural and contaminated aqueous ecosystems, and possibly in human body fluids. In this study, solid metal arsenates were dissolved isothermally in solutions with different molar concentrations of arsenic acid. The saturated solutions were analysed and the results processed to derive the solubility products (Ksp) for solid phases and association constants (K) for metal arsenate ion-pairs. Ion chromatography was used to confirm the presence of ion-pairs, some of which had never before been considered. Association constants were determined for the following ion-pairs: FeHAsO4+ (log K = 4.88), CoHAsO40 (log K = 1.50), ZnHAsO40 (log K = 3.28), SrH2AsO4+ (log K = 1.72), and Ag2H2AsO4+ (log K = 4.50). The following metal ions apparently do not form stable complexes with HAsO42–: Cd2+, Cr3+, Cu2+, Mg2+, Mn2+, Ni2+, Pb2+, and Sn2+. Standard state solubility products (Ksp°) were redetermined for the following compounds: Ag3AsO4, Cd3(AsO4)2, Co3(AsO4)2, CrAsO4, Cu3(AsO4)2, FeAsO4, Mg3(AsO4)2, MnHAsO4, NiHAsO4, PbHAsO4, Sn3(AsO4)2, Sr3(AsO4)2, Zn3(AsO4)2·Zn3(AsO4)2·8H2O (koettigite), Cu2Al7(AsO4)4(OH)13·12H2O (ceruleite), and Pb2CuAsO4CrO4OH (fornacite). Our results show the formation of ion-pairs for some metal arsenates and indicate that previous studies have overestimated the solubilities of many arsenates.

Effects of substituents on ion-association properties. II. 1H N.M.R. studies of substituted pyridinium and tetraalkylammonium Bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) in non-aqueous solvents

1981 ◽  
Vol 34 (11) ◽  
pp. 2321 ◽  
Author(s):  
N Tsao ◽  
Y Lim
Keyword(s):  
Dielectric Constant ◽  
Complex Anion ◽  
Ion Pairs ◽  
Ion Association ◽  
Ion Pair ◽  
Association Constants ◽  
Ionic Clusters ◽  
Isotropic Shift ◽  
Large Size ◽  
Pyridinium Cations

A series of nine compounds containing quaternary ammonium and substituted pyridinium cations and the bis(4-methylbenzene-1,2-dithiolato)cobaltate(III) complex anion have been prepared andtheir ion-pair properties studied by lH n.m.r. spectroscopy. Their concentration association constants in nitrobenzene at 307 K range from 9 to 20. In the pyridinium series of ion pairs, it is concludedfrom the measured isotropic shift ratios that methyl substituents at the meta and para positions favour a geometry where the anion is tilted towards the ring of the cation but the ortho substituents push the anion away from the ring. In the methyltrioctylammonium ion pair, there is linear correlation between the observed isotropic shift of the N-methyl or the N-methylene protons and the dielectric constant of the solvents (E) from 4.56 to 12.3 for the 0.06, 0.09 and 0.12 M solutions. Its implication is discussed in terms of the formation of the ionic clusters of sufficiently large size.

Application of 59Co NMR to the investigation of interactions between cobalt sepulchrate and various counterions

1991 ◽  
Vol 69 (3) ◽  
pp. 567-569 ◽  
Author(s):  
João Sotomayor ◽  
Helena Santos ◽  
Fernando Pina
Keyword(s):  
Quantum Yield ◽  
Association Constant ◽  
Chemical Shifts ◽  
Cobalt Complex ◽  
Ion Pairs ◽  
Formation Constants ◽  
Ion Pair ◽  
Association Constants ◽  
Quantum Yields ◽  
True Quantum

Association constants for the ion pairs formed between [Co(Sep)]3+ and the anions fluoride, chloride, bromide, iodide, perchlorate, and oxalate were obtained from the chemical shifts of the 59Co resonance that occur upon addition of such anions to solutions of the cobalt complex. The usefulness of 59Co NMR to obtain formation constants, in order to calculate the "true" quantum yields for the ion pairs, is discussed. Key words: association constant, cobalt sepulchrate, ion pair, 59Co NMR, quantum yield.

Chemistry of gaseous ion pairs produced by thermal collisions

1980 ◽  
Vol 77 ◽  
pp. 759-768 ◽  
Author(s):  
R. Stephen Berry
Keyword(s):  
Ion Pairs
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