The effect of counterion on alkali ion-crown complex formation: A near-paradox in dissociating solvents

1983 ◽  
Vol 48 (9) ◽  
pp. 2509-2517
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Ion Pairing ◽  
Ethanolic Solution ◽  
Dramatic Effect ◽  
Widespread Belief ◽  
Alkali Ion

Contrary to the widespread belief that counterion influences stability of charged complexes only in poorly solvating media, a dramatic effect of anion was discovered, ebulliometrically, in 0.6 molal M+X--C2H5OH (M = K, Na, Li; X = SCN, OC2H5) and in 0.6 molal M+X--H2O (M = K; X = SCN, OH) solution upon complexing with 18-crown-6,15-crown-5 and 12-crown-4. Out of the nine crown-MSCN combinations examined in the ethanolic solution, seven yielded 1 : 1 (18-crown-6-KSCN, 18-crown-6-NaSCN, 15-crown-5-NaSCN, 15-crown-5-LiSCN, 12-crown-4-KSCN) or 2 : 1 (15-crown-5-KSCN, 12-crown-4-NaSCN) complexes quantitatively, whereas the corresponding crown-MOC2H5 combinations did not complex at all or the complexation was very incomplete. An analogous situation was found in the aqueous solution, with KSCN complexing 18-crown-6 quantitatively or 15-crown-5 and 12-crown-4 partly, whereas KOH did not yield complexes with any of the three crowns. Evidence is presented that the observed effect of anion does not originate from ion-pairing.

Anion effect on alkali ion-crown complex formation in a moderately concentrated solutions: A sensitive probe of hidden interionic interactions operating in dissociating protic solvents

1990 ◽  
Vol 55 (5) ◽  
pp. 1149-1161
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Charge Density ◽  
Macrocyclic Ligand ◽  
Simple Explanation ◽  
Anion Effect ◽  
Protic Solvents ◽  
The Individual ◽  
Alkali Salts ◽  
Alkali Ion

A powerful anion effect destabilizing alkali ion-crown complex formation has been found to operate in moderately concentrated protic (H2O, CH3OH, C2H5OH) solution, following the order HO- > AcO- > Cl- > Br- > NO3- > I- > NCS-. Evidence is provided that the observed effect does not originate from ion-pairing. A simple explanation is provided in terms of concordant hydrogen bond bridges of exalted stability between the gegenions, M+···OR-H···(OR-H)n···OR-H···A-. It is proposed that encapsulation of alkali ion by the macrocyclic ligand leads to a dissipation of the cation charge density destroying its ability to participate in the hydrogen bond bridge. An opposition against the alkali ion-crown complex formation arises accordingly in the solution in dependence on strength of the hydrogen bridge; for a given cation, the hydrogen bond strength increases with increasing anion charge density from NCS- to HO-(RO-). It is pointed out, at the same time, that the observed anion effect does not correlate with the known values of activity coefficients of the individual alkali salts which are almost insensitive to anion variation under the investigated conditions. As a resolution of the apparent paradoxon it is proposed that, in absence of the macrocyclic ligand, the stabilizing (concordant) bonding between the gegenions is nearly balanced by a destabilizing (discordant) hydrogen bonding between the ions of same charge (co-ions). Intrinsic differences among the individual salts are thus submerged in protic solvents and become apparent only when the concordant bonding is suppressed in the alkali ion-crown complex formation.

Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

1965 ◽  
Vol 18 (5) ◽  
pp. 651 ◽  
Author(s):  
RW Green ◽  
PW Alexander
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Complex Formation ◽  
Distribution Coefficient ◽  
Dilute Aqueous Solution ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Beryllium Complexes ◽  
Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

Hydration and contact ion pairing of Ca2+ with Cl− in supercritical aqueous solution

2006 ◽  
Vol 125 (9) ◽  
pp. 094507 ◽  
Author(s):  
John L. Fulton ◽  
Yongsheng Chen ◽  
Steve M. Heald ◽  
Mahalingam Balasubramanian
Keyword(s):  
Aqueous Solution ◽  
Ion Pairing ◽  
Supercritical Aqueous Solution

Complex Formation in the Ternary System Tl(III)−CN-−Cl-in Aqueous Solution. A205Tl NMR Study

1996 ◽  
Vol 35 (24) ◽  
pp. 7074-7081 ◽  
Author(s):  
Katja E. Berg ◽  
Johan Blixt ◽  
Julius Glaser
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Ternary System ◽  
Nmr Study

scholarly journals Chemical Properties of Element 105 in Aqueous Solution: Halide Complex Formation and Anion Exchange into Triisoctyl Amine

1989 ◽  
Vol 48 (3-4) ◽  
Author(s):  
J. V. Kratz ◽  
H. P. Zimmermann ◽  
U. W. Scherer ◽  
M. Schädel ◽  
W. Brüchle ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Anion Exchange ◽  
Chemical Properties ◽  
Halide Complex

Uranyl(VI) complexes with alpha-substituted carboxylic acids in aqueous solution

2003 ◽  
Vol 91 (1) ◽  
Author(s):  
H. Moll ◽  
G. Geipel ◽  
T. Reich ◽  
G. Bernhard ◽  
Th. Fanghänel ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Carboxylic Acids

SummaryThe complex formation in the binary uranium(VI)-glycolate, -

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