Anion oxyanions

Monatomic cations with constant charges Monatomic cations with variable charges Polyatomic cations Monatomic anions Oxyanions... 

Common anions may be grouped as follows monatomic anions, oxyanions, and special anions. There are special endings for the first two groups the third group is small enough to be memorized. 

The coefficients a, and b are dependent on temperature and the type of ion (cations, OH- and simple anions, oxyanions and acid oxyanions) and have been established by Criss and Cobble by analyzing available experimental data. SiggCabsolute) is the 298°K entropy on an absolute sca e corresponding to the partial molal entropy of H (aq) as -5.0 cal deg" mole-1 at 298°K. The absolute and conventional partial molal entropy for any ion are related by... 

Adsorption of simple inorganic anions, oxyanions and organic ions on iron oxides has been widely investigated (see Tables 11.1 and 11.2). Anions are ligands, i.e. they possess one or more atoms with a lone pair of electrons and so can function as the donor in a coordinate bond. Ligands may adsorb on Fe oxides either specifically or non specifically. 

Phosphates are compoimds that contain oxyanions of phosphorus(V), ranging from the simple orthophosphate group to condensed chain, ring, and network anions. Oxyanions of phosphorus in lower oxidation states such as phosphite, HP03, are also known. 

Although a hydroxyl group strongly activates an aromatic ring toward electrophilic attack an oxyanion substituent is an even more powerful activator Electron delocaliza tion m phenoxide anion leads to increased electron density at the positions ortho and para to oxygen... 

The chemistry of vanadium compounds is related to the oxidation state of the vanadium. Thus, V20 is acidic and weaMy basic, VO2 is basic and weaMy acidic, and V2O2 and VO are basic. Vanadium in an aqueous solution of vanadate salt occurs as the anion, eg, (VO ) or (V O ) , but in strongly acid solution, the cation (V02) prevails. Vanadium(IV) forms both oxyanions ((V O ) and oxycations (VCompounds of vanadium(III) and (II) in solution contain the hydrated ions [V(H20)g] and [V(H20)g], respectively. 

In principle, numerous reports have detailed the possibility to modify an enzyme to carry out a different type of reaction than that of its attributed function, and the possibility to modify the cofactor of the enzyme has been well explored [8,10]. Recently, the possibility to directly observe reactions, normally not catalyzed by an enzyme when choosing a modified substrate, has been reported under the concept of catalytic promiscuity [9], a phenomenon that is believed to be involved in the appearance of new enzyme functions during the course of evolution [23]. A recent example of catalytic promiscuity of possible interest for novel biotransformations concerns the discovery that mutation of the nucleophilic serine residue in the active site of Candida antarctica lipase B produces a mutant (SerlOSAla) capable of efficiently catalyzing the Michael addition of acetyl acetone to methyl vinyl ketone [24]. The oxyanion hole is believed to be complex and activate the carbonyl group of the electrophile, while the histidine nucleophile takes care of generating the acetyl acetonate anion by deprotonation of the carbon (Figure 3.5). 

The incorporation of anions, as for example, S04 , CO2-, etc., makes leaching possible through the formation of stable uranyl (VI) oxyanions. In sulfate leaching, an observation of the potential-pH diagram for the uranium system reveals that uranium species in solution may be in the form of cations U02+, neutral species U02(S04)2 or anions U02(S04)4-. The oxidation of uraninite, U02, in acid solutions, transforming U(IV) to U(VI), yields soluble uranyl sulfate through the reaction as shown below ... 

Tosylate is displaced by weak oxyanions with little elimination in aprotic solvents, providing alternative routes to polymer-bound esters and aryl ethers. Alkoxides, unfortunately, give significant functional yields of (vinyl)polystyrene under the same conditions. Phosphines and sulfides can also be prepared from the appropriate anions (57), the latter lipophilic enough for phase-transfer catalysis free from poisonning by released tosylate. 

Oxyanions consist of an atom of an element plus some number of atoms of oxygen covalently bonded to it. The name of the anion is given by the name of the element with its ending changed to either -ate or -ite. In some cases, it is also necessary to add the prefix per- or hypo- to distinguish all the possible oxyanions from one another. For example, there are four oxyanions of chlorine, which are named as follows ... 

The oxyanion containing Zn2+, Zn022-, is known as a zincate, and it equivalent to Zn(OII)42, which is named as the tetrahydroxozincate(II) anion (see Chapter 16). From these reactions, it is clear that ZnO can react as either an acidic or basic oxide and it is therefore known as an amphoteric oxide. In essence, there are some oxides that are clearly acidic, some that are dearly basic, and some that are in between. There is, in fact, a continuum of acid-base character for the oxides of elements that is shown in Figure 9.2. 

Several approaches have been used to overcome the stereochemical difficulties for intramolecular "alkyl transfer." One of these is to use a "trapping agent" in the reaction mixture with which the oxyanion site of the intermediate can react. A silyl halide works nicely for this purpose the halide anion facilitates the required dealkylation.206-210... 

Soils with AEC can be expected to exchange anions in the same way. However, in many soils, anions are present as oxyanions, which often react with soil components to form permanent covalent bonds and thus do not act as exchangeable anions. Phosphate anions are excellent examples of this type of interaction [11],... 

It is reasonable to expect that because anions and most colloidal particles in temperate region soils have a negative charge, they will repel each other. The consequence is that anions will pass through soil and will not be adsorbed or even retarded. For the simple anions and some of the oxyanions, this is exactly what happens. All the halides, nitrite, nitrate, bicarbonate, and carbonate act in this fashion. However, there are some oxyanions that do not act as expected, and chief among them is phosphate. 

Simple anions are those that exist only in one oxidation state in soil and generally are only assodated with water. Complex anions are typically oxyanions of nonmetals, although molybdenum occurs as an oxyanion. 

Many important soil components are not present as simple cations or anions but as oxyanions that include both important metals and nonmetals. The most common and important metal oxyanion is molybdate (Mo042 ). The most common and important nonmetal oxyanions are those of carbon (e.g., bicarbonate [HC03 ] and carbonate [C032-]), nitrogen (e.g., nitrate [N03 ] and nitrite [NQ2 ]), and phosphorus (e.g., monobasic phosphate [H2P04 ], dibasic... 

Give some examples of anions including oxyanions that are common in soil. 

Organo-modified natural zeolites as new tailored natural materials for removal of cations, anions and even organic pollutants may present fairly large potential for water utility companies. The topic of this study was to examine the oxyanions removal from waters by octadecylammonium-enriched inland clinoptilolite. The 18-carbon chain consisting surfactant attached on the clinoptilolite surface, as to the organic acids of living bodies comparable substances, makes the treatment process economic on scale and cost-effective as well.7... 

Some approach to tailor a new natural anion exchanger from ODA-modified clinoptilolite was studied. We verified repeatedly clinoptilolite enhanced oxyanion uptake mechanism after regeneration and so far confirmed the feasibility at laboratory level. To set this process for water treatment in recycling operation, a pilot plant research is necessary to accomplish. In contrast to clay s properties, which surface have been usually... 

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