Anionic stability decreasing

Reversible step transfer of up to 6 electrons per one molecule to form anion radicals is observed in the cathodic polarization of C6o fullerene solutions [6], Anion particles are stable in aprotic media, however in the general case anion stability decreases with increasing charge [7]. The number of observed steps depends on the medium and experimental conditions. The literature analysis [8-10] has revealed that the use of different solvent systems, base electrolytes and electrodes results in considerable variations in redox potentials for the most extensively studied pairs of C(JC , C(,fC(f2, C(,fCeo"3. 

All three acids disproportionate in water, the rate and products of this reaction being influenced by temperature, concentration, and solution pH. HOCl is more stable than HOBr or HOI. Base converts the acids to the anions, which disproportionate less readily. Anion stability decreases in the order C10 > BrO > lO". 

Reaction (11.4) is really a disproportionation reaction of the halate(I) anion 3XO 2X -E XO. ) Reaction (11.3) is favoured by the use of dilute alkali and low temperature, since the halate(I) anions, XO are thermally unstable and readily disproportionate (i.e. reaction (11.4)). The stability of the halate(I) anion, XO , decreases from chlorine to iodine and the iodate(I) ion disproportionates very rapidly even at room temperature. 

If the nucleophilicity of the anion is decreased, then an increase of its stability proceeds the excessive olefine can compete with the anion as a donor for the carbenium ion, and therefore the formation of chain molecules can be induced. The increase of stability named above is made possible by specific interactions with the solvent as well as complex formations with a suitable acceptor 112). Especially suitable acceptors are Lewis acids. These acids have a double function during cationic polymerizations in an environment which is not entirely water-free. They react with the remaining water to build a complex acid, which due to its increased acidity can form the important first monomer cation by protonation of the monomer. The Lewis acids stabilize the strong nucleophilic anion OH by forming the complex anion (MtXn(OH))- so that the chain propagation dominates rather than the chain termination. 

Then, substitution of the sulfur atom of Cys with an oxygen would greatly decrease the rate of reaction, because nucleophilicity, anion-stabilizing effect and proton-donating ability of OH group are far smaller than that of an SH group. 

It is interesting to note that direct synthesis gives bis(phthalocyanine) complexes oftrivalent metals as anionic species, which are gradually transformed into neutral paramagnetic species under exposure to air. The stability of the anionic species decreases in the series oflanthanide complexes with a decrease in the ionic radii of the elements [135]. 

The EPA properties of the metal ion decrease with increasing donicity of the solvent so that the stabilizing effect of the radical anion is decreased the redox potential is shifted to more negative values by increasing solvent donicity (Fig. 2). 

A few mixed compounds of Eu3+ containing dibenzoylmethide ion and carboxylate anions (acetate, propionate and benzoate) of the general formula, (DBM)2EuOCOR, have been isolated [43Z], Thermogravimetric investigations on these complexes show that their heat stability decreases in the order acetate > propionate > benzoate. The melting points of... 

The thermal stability of the sulfate anion varies with the cation, as was described for the carbonates, i.e., stability decreases with increasing polarizing power of the cation. Thus small cationic size and high charge promote decomposition. The primary decomposition is to the oxide and S03, accompanied by decomposition of that gas to S02 and 02. Thus in a closed system there will also be two simultaneous equilibria ... 

The corresponding dependence of cation complex stability on the anion differs profoundly from that of most other cation receptors such as cyclophanes or calix-arenes [16]. For these cation complex stability decreases on changing the anion from picrate through iodide to tosylate, a dependence that has been attributed to ion-pair aggregation in non-polar solvents. Because the interaction of quaternary ammonium ions with tosylate or iodide in chloroform is considerably stronger than with picrate, cation complexes in the presence of the latter anion are usually more stable. Only when iodide or tosylate cooperatively contributes to cation binding, as in 3 or in some recently described calixarene derivatives [17], is reversal of this order observed. 

Scheme 2.12 Electron-donating groups decrease acidity by decreasing anionic stability.

As [Fe l and [Mn ] are increasing, so is 0 and E decreases. At one point the two potentials are going to invert, that is, E 1 < E(2 and reaction (2) is going to be more favourable. To avoid the side reaction we have to keep (1) > (2). If the phosphate anion stabilizes Fe , that means that through complexation we can make the Fe /Fe potential more negative, meaning at (1) becomes more positive and reaction (1) more favourable (see... 

T, must be taken. Stability decreases with increasing atomic number of the group-IIA element and aryl are more stable than alkyl. Donors exert a stabilizing effect and, therefore, solvents such as tetrahydrofuran (THE) or pyridine (PY) are expedient for preparation and handling them. Diethyl ether is not sufficiently basic to impart adequate stability. The reactivity can be correlated with ionic character in the Pb-group-IIA element bond, the organolead moiety being anionic. 

DSC, reported that SCN, another chaotropic anion, stabilizes BSA in the same conditions. It is known that SCN binds strongly to BSA [191]. We observed [195] that Ca2+ and Mg2+ decrease QD and Tm of ribulose 1,5-diphosphate carboxylase (Rubisco) to a limited extent but in a definite and steady way as their concentration increases over the ionic strength range 0-0.3 mol/L Na+ and NH+4 had an opposite effect. In the case of Rubisco, specificity of the effect of Ca2+ and Mg2 + is supported by the fact that these cations are known to bind to the protein and to affect its enzymatic activity by inducing structural changes. Specific effects of Na+ and Ca2+ are also observed by DSC on the heat stability of a-lactalbumin [190] they result in a linear increase of QD with the cation/protein molar ratio up to 1, followed by a plateau (Fig. 7). 

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