Exchange of anions

They can be used in acid solution for the exchange of anions, for example ... 

Exchange diffusion systems are present in the membrane for exchange of anions against OH ions and cations against H ions. Such systems are necessary for uptake and output of ionized metaboUtes while preserv-... 

These are usually reactions of anhydrous transition and B metal halides with dry alkali metal salts such as the sulphides, nitrides, phosphides, arsenides etc. to give exchange of anions. They tend to be very exothermic with higher valence halides and are frequently initiated by mild warming or grinding. Metathesis is... 

A short review by Taylor (1997) illustrates that bivalent cations may be exchanged for Ca2+, trivalent cations and Si(OH)4 for Al3+ and a number of anions have been exchanged for SOl ions. To date most investigations of ettringite as a heavy metal or metalloid binding agent have considered the exchange of anions for SOl. This will be discussed in detail later in the text. 

The hypothesis is adopted that in every case of interaction between a 44 donor99 and an 64 acceptor99 there occurs an exchange of anions from the former for an equal number of electrons from the latter. This exchange is followed by the union of the two residues with formation of the coloured complex, the extent to which the latter is formed being governed by temperature and concentration as well as by the nature of the interactants. Substances acting as 14 donors 99 or 44 acceptors," but... 

While some molybdenum complexes such as Mo03(dien) were found to be inactive,236 the rates of molybdenum-catalyzed epoxidation of alkenes were found to be independent of the structure of the complex used, after an induction period representing the time for exchange of anionic ligands by the alkyl hydroperoxide. cis-Dioxomolybdenum(VI) diolates such as (78) were isolated... 

By coupling with bromine under mild conditions 4-(4 -dimethylamino-phenyl)tellurapyrylium borotetrafluoride 25 affords 10-Te-4 tellurane 115 in 90-97% yield (86MI2). When bromine is taken in excess, an exchange of anions (BF Brj) in 115 takes place. The structure of the compound 115 (X = Brj) has been established by X-ray analysis. 

And when it comes to active sites, the issue of adsorption or ion exchange of anions on a positively charged carbon surface has been, and still is to some extent, highly controversial (see Sections... 

Anion adsorption and then the exchange of anions mainly takes place on the protonated surface sites of silicates and other oxides (e.g., iron, manganese oxides) and hydroxides, as well as on the positive functional group (e.g., protonated amino groups) of humic substances. It is directed by electrostatic forces. The degree of anion exchange of rocks and soils is usually much less than that of cation exchange. 

Exchange of anionic substituents and generation of a transient carbonium ion are considered here. For some other, mechanistically less well understood reactions, see Section 4.12.3.3 which deals with the reactivity of substituents. 

Anion exchange resins High-molecular-weight polymers to which amine groups are bonded. They permit the exchange of anions in solution for hydroxide ions from the exchanger. 

Pursuing this idea further, it is seen that anhydride formation in the sugars resolves itself into an exchange of anions on a carbonium cation,... 

The stability of these bismuthonium salts (82) - (85) depends on the nature of the anionic counterpart and of the fourth ligand. The allyl derivatives (84) are too unstable to be isolated. On the other hand, the tetrafluoroborate salts of the derivatives of the three other types of onium compounds are thermally stable. Ligand coupling- type products are formed with more nucleophilic anions, for example during the attempted exchange of anion with bromide or iodide, or during the slow decomposition of a solution of bismuthonium tosylates in chloroform. ... 

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