Other anions

Trace amounts of chromate ions adsorbed on magnetite are reduced to Cr by the surface Fe ions (Music et al., 1986 Peterson et al., 1996, 1997a Kendlewicz et al., 

A solid state reaction in which the surface layers of magnetite are converted into maghemite appears to be involved as more chromate is adsorbed, further reduction is halted (Peterson et al., 1996). XAS showed that although adsorbed chromate was not reduced on the (112) plane of hematite, small amounts were reduced on (001) it was suggested that some Fe had been produced on the latter plane during annealing under vacuum (Kendlewicz et al., 1999). 

Chromate adsorbed from solution by green rust was reduced to Cr with the green rust being simultaneously converted to ferrihydrite or possibly a Cr substituted ferrihydrite (Loyaux-Launiezak et al., 2000). 

The selenite and sdenate ions illustrate the effect of oxidation state on adsorption behaviour. The selenite ion (SeO ) adsorbs strongly and specifically on goethite and shifts the iep of both goethite and ferrihydrite to lower pH values (Su and Suarez, 

Adsorption of ferricyanide (a contaminant of sites of former gas plants) on goethite decreases with rising pH and is dependent on ionic strength it is fully reversible and is thought to involve both inner and outer sphere complexes. Adsorption of ferrocyanide on goethite involves initial formation of inner sphere complexes followed by precipitation of a Berlin Blue-like phase on the goethite surface (Rennert and Mansfeldt, 2001). 

The electrophilic silicon can even bind nucleophilic compounds (ethers, amines, etc.) yielding complexes which initiate polymerizations of vinyl compounds [98] 

By interaction of alkyllithium with 2-methylthiirane, active centres are produced in the form RS Li+. With monomer these centres yield polypropy-lenesulphide. In the presence of lithium tert.-alcoholates, complexes of the shape 

Thus the modification of centres by tertiary alcoholates is not limited to MMA polymerization. 

The use of the silyl anion derivative (CH30)n (CH3)3 Si Na+ [100] in the role of an active centre is as yet only possibility. The usefulness of theoretical studies of some centres of this kind, for example of those formed during phos-phazene polymerization (see Chap. 2, Sect. 1.1), should increase with time. 

Anionic polymerizations of heterocycles differ considerably from polymerizations of unsaturated monomers. 

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A third method for generating ions in mass spectrometers that has been used extensively in physical chemistry is chemical ionization (Cl) [2]. Chemical ionization can involve the transfer of an electron (charge transfer), proton (or otlier positively charged ion) or hydride anion (or other anion). 

The first step is the interaction of the basic catalyst with the ester to produce the carbanion (I) the carbanion so formed then attacks the carbonyl carbon of a second molecule of ester to produce the anion (II), which is converted to ethyl acetoacetate (II) by the ejection of an ethoxide ion. Finally (III) reacts with ethoxide ion to produce acetoacetic ester anion (IV). This and other anions are mesomeric thus (IV) may be written ... 

The purpose of the ether may be to coordinate with the alaminium hydride and to facilitate the forward reaction in the first instance subsequently coordination may occur with other anions available in the solution. 

Heteroatomic and Other Anions. A few heteroatomic anions have names ending in -ide. These are... 

Dowex 1-X4 1.0 0.70 Strongly basic anion exchanger with S-DVB matrix for separation of organic acids, nucleotides, phosphoinositides, and other anions. Molecular weight exclusion is <1400. 

Actinide ions of the 111, IV, and VI oxidation states can be adsorbed by cation-exchange resins and, in general, can be desorbed by elution with chloride, nitrate, citrate, lactate, a-hydroxyisobutyrate, ethylenediaminetetraacetate, and other anions (11,12). 

A.lkyl Sulfosuccinate Half Asters. These detergents are prepared by reaction of maleic anhydride and a primary fatty alcohol, followed by sulfonation with sodium bisulfite. A typical member of this group is disodium lauryl sulfosucciaate [26838-05-1]. Although not known as effective foamers, these surfactants can boost foams and act as stabilizers when used ia combination with other anionic surfactants. In combination with alkyl sulfates, they are said to reduce the irritation effects of the latter (6). 

Ion exchange is a process in which cations or anions in a Hquid are exchanged with cations or anions on a soHd sorbent. Cations are interchanged with other cations, anions are exchanged with other anions, and electroneutraUty is maintained in both the Hquid and soHd phases. The process is reversible, which allows extended use of the sorbent resin before replacement is necessary. 

Salt forms of a strong base anion exchangerare used to remove other anions for which the resin has greater selectivity. 

Uranium ores are leached with dilute sulfuric acid or an alkaline carbonate [3812-32-6] solution. Hexavalent uranium forms anionic complexes, such as uranyl sulfate [56959-61-6], U02(S0 3, which are more selectively adsorbed by strong base anion exchangers than are other anions in the leach Hquors. Sulfate complexes are eluted with an acidified NaCl or ammonium nitrate [6484-52-2], NH NO, solution. Carbonate complexes are eluted with a neutral brine solution. Uranium is precipitated from the eluent and shipped to other locations for enrichment. Columnar recovery systems were popular in South Africa and Canada. Continuous resin-in-pulp (RIP) systems gained popularity in the United States since they eliminated a difficult and cosdy ore particle/leach hquor separation step. 

For continuing polymerization to occur, the ion pair must display reasonable stabiUty. Strongly nucleophilic anions, such as C/ , are not suitable, because the ion pair is unstable with respect to THE and the alkyl haUde. A counterion of relatively low nucleophilicity is required to achieve a controlled and continuing polymerization. Examples of anions of suitably low nucleophilicity are complex ions such as SbE , AsF , PF , SbCf, BE 4, or other anions that can reversibly coUapse to a covalent ester species CF SO, FSO, and CIO . In order to achieve reproducible and predictable results in the cationic polymerization of THE, it is necessary to use pure, dry reagents and dry conditions. High vacuum techniques are required for theoretical studies. Careful work in an inert atmosphere, such as dry nitrogen, is satisfactory for many purposes, including commercial synthesis. 

Minerals of sodium sulfate occur naturally throughout the world. The deposits result from evaporation of inland seas and terminal lakes. Colder climates, such as those found ia Canada and the former Soviet Union, favor formation of mirabilite. Warmer climates, such as those found ia South America, India, Mexico, and the western United States, favor formation of thenardite. In areas where other anions and cations are present, double salts can be found of the kiads shown ia Table 2, which Hsts nearly all naturally occurring minerals containing sodium sulfate. Except for mirabilite, thenardite, and astrakanite, these mineral deposits play a minor role ia sodium sulfate production. 

Sodium and chloride may be measured using ion-selective electrodes (see Electro analytical techniques). On-line monitors exist for these ions. Sihca and phosphate may be monitored colorimetricaHy. Iron is usually monitored by analysis of filters that have had a measured amount of water flow through them. Chloride, sulfate, phosphate, and other anions may be monitored by ion chromatography using chemical suppression. On-line ion chromatography is used at many nuclear power plants. 

Ethoxylation of alkyl amine ethoxylates is an economical route to obtain the variety of properties required by numerous and sometimes smaH-volume industrial uses of cationic surfactants. Commercial amine ethoxylates shown in Tables 27 and 28 are derived from linear alkyl amines, ahphatic /-alkyl amines, and rosin (dehydroabietyl) amines. Despite the variety of chemical stmctures, the amine ethoxylates tend to have similar properties. In general, they are yellow or amber Hquids or yellowish low melting soHds. Specific gravity at room temperature ranges from 0.9 to 1.15, and they are soluble in acidic media. Higher ethoxylation promotes solubiUty in neutral and alkaline media. The lower ethoxylates form insoluble salts with fatty acids and other anionic surfactants. Salts of higher ethoxylates are soluble, however. Oil solubiUty decreases with increasing ethylene oxide content but many ethoxylates with a fairly even hydrophilic—hydrophobic balance show appreciable oil solubiUty and are used as solutes in the oil phase. 

Adsorption Isotherms. EquiUbrium dialysis studies indicate around 10 repeat VP units (base moles) are required to form favorable complexes (89,90). This figure can rise to several hundred for methyl orange and other anions depending on stmcture (91,92). 

The tetramer exists in two-molal zirconium chloride and nitrate solutions, but it polymerizes into cross-linked chains on hydrolysis (190—191) in strong acid solutions, the hydroxyl bridges can be replaced by other anions to form trimers (192) and monomers (192—193). 

Carbonates. Basic zirconium carbonate [37356-18-6] is produced in a two-step process in which zirconium is precipitated as a basic sulfate from an oxychloride solution. The carbonate is formed by an exchange reaction between a water slurry of basic zirconium sulfate and sodium carbonate or ammonium carbonate at 80°C (203). The particulate product is easily filtered. Freshly precipitated zirconium hydroxide, dispersed in water under carbon dioxide in a pressure vessel at ca 200—300 kPa (2—3 atm), absorbs carbon dioxide to form the basic zirconium carbonate (204). Washed free of other anions, it can be dissolved in organic acids such as lactic, acetic, citric, oxaUc, and tartaric to form zirconium oxy salts of these acids. 

Lithium hypochlorite is used in I I laundry detergents and I I dry laundry bleaches. Like sodium hypochlorite, it does not precipitate soaps and other anionic detergents. However, lithium hypochlorite is an expensive source of available chlorine and not much is used for bleaching. Its principal use is as a shocking agent for swimming pool disinfection. 

Chlorides, which are ubiquitous in nature, play an important role in the corrosion of metals. Chlorides and other anions also play an important role in locali2ed corrosion, ie, the breakdown of the insoluble protective reaction product films, eg, passive films, that prevent corrosion of the underlying metal. A variety of mechanisms attempting to explain the role of chloride in general and in locali2ed corrosion have been proposed (23—25). 

Only the anion (239) is susceptible to C-alkylation in the 4-position. The two other anions (240) and (241) can only give rise to O-and A-substituted derivatives which result in the asymmetry of Scheme 19. 

As metal ion concentration increases in the crevice, a net positive charge accumulates in the crevice electrolyte. This attracts negatively charged ions dissolved in the water. Chloride, sulfate, and other anions spontaneously concentrate in the crevice (Figs. 2.4 and 2.5). Hydrolysis produces acids in the crevice, accelerating attack (Reactions 2.5 and 2.6). Studies have shown that the crevice pH can decrease to 2 or less in salt solutions having a neutral pH. 

The hydroxyl ions migrate inward, attracted by the positive charge that is produced by the ferrous ion generated near the corroding surface (Fig. 3.4). Other anions such as carbonate, chloride, and sulfate also concentrate beneath the shell. Carbonate may react with ferrous ions to form siderite (FeCOa) as in Reaction 3.4 (Fig. 3.7) ... 

Cellex D and other anionic celluloses are washed with 0.25M NaCl/0.25M NaOH solution, then twice with deionised water. This is followed with 0.25M NaCl and then washed with water until chloride-free. The Cellex is then equilibrated with the desired buffer as above. 

B H +3 formed by removal of 1 bridge proton from B H +4, e.g. BsHg", BioHi3 other anions in this series such as B4H7" and BgHi2 are known though the parent boranes have proved too... 

Isolated B(OH)3 groups, or polymers of these, may exist in the presence of other anions. 

The chloride ion is readily replaced by other anions to give, for example, the orange-yellow [S4N3]Br, bronze-coloured [S4N3]SCN, [S4N3]N03, [S4N3]HS04, etc. 

IS further extended by the replacement of X by other anionic or neutral ligands. The inertness of the compounds makes such substitution reactions slow (taking hours or days to attain equilibrium) and, being therefore amenable to examination by conventional analytical techniques, they have provided a continuing focus for kinetic studies. The forward (aquation) and backward (anation) reactions of the pentaammines ... 

Many other anions can then be introduced by metathetical reactions with the appropriate silver salt ... 

Other anion-forming substances in which hydration has been established include 1- and 3-methyl-2-pteridinone, 3,6,7-trimethyl-2-pteridinone, and 5-methyl-6-pteridinone ... 

For reasons discussed in Section VI, a survey of the purine series (29) is being made in this Department, but so far no example (including 2-hydroxy- and 8-trifluoromethyl-2-hydroxy-purine) of covalent hydration has come to light. An examination of ionization constants disclosed no apparent anomalies, although the interpretation is made more difficult by the ease of anion formation in the 9-position, which often competes with that from other anionic substituents. The only abnormal spectrum seems to be that of the anion of 2-mercaptopurine which is being further examined. 

The smooth conversion of the enol acetate (151) into an A -acyl derivative (152) under extremely mild conditions points to the high acylating capacity of these esters. This cleavage of isoxazolium salts is also caused by other anions of carboxylic acids, and thus they can be readily converted to reactive enol esters. A very convenient and specific synthesis of peptides due to Woodward et is based on... 

The alkylation process possesses the advantages that (a) a wide range of cheap haloalkanes are available, and (b) the substitution reactions generally occur smoothly at reasonable temperatures. Furthermore, the halide salts formed can easily be converted into salts with other anions. Although this section will concentrate on the reactions between simple haloalkanes and the amine, more complex side chains may be added, as discussed later in this chapter. The quaternization of amines and phosphines with haloalkanes has been loiown for many years, but the development of ionic liquids has resulted in several recent developments in the experimental techniques used for the reaction. In general, the reaction may be carried out with chloroalkanes, bromoalkanes, and iodoalkanes, with the reaction conditions required becoming steadily more gentle in the order Cl Br I, as expected for nucleophilic substitution reactions. Fluoride salts cannot be formed in this manner. 

Since the hydroxyl anion is involved in the mechanism given before, the implication is that other anions may also take part in the dissolution process, and that the effect of various chemicals may be interpreted in the light of the effect of each anion species. Most studies have been in solutions of sulphuric and hydrochloric acids and typically the reaction postulated for active dissolution in the presence of sulphuric acid is ... 

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