Chloride aqueous chemistry

Titanium forms dihalides TiXj, for example titanium(II) chloride, formed by heating titanium metal and the tetrachloride to about 1200 K. TiCl2 is a black solid, which disproportionates on standing to TiCl4 + Ti. Since it reduces water to hydrogen, there is no aqueous chemistry for titanium(II). A solid oxide TiO is known. 

Hydroxyl Compounds. The aqueous chemistry of zirconium is complex, and in the past its understanding was compHcated by differing interpretations. In a study of zirconium oxide chloride and zirconium oxide bromide, the polymeric cation [Zr4(OH)g (H20)jg was identified (189) the earlier postulated moiety [Zr=0] was discarded. In the tetramer, the zirconium atoms are coimected by double hydroxyl bridges (shown without the coordinating water molecules) ... 

An even more serious problem can arise when dissolved species expected to predominate at high temperatures are undetectable at 25°C or are only present at concentrations which are too low for them to be adequately characterized thermodynamically. Examples are certain transition metal chloro-complexes (9,10) and mixed complexes of such metals with hydroxide and another ligand (11,12). Thus it seems that chloride complexing so alters the aqueous chemistry of copper and gold that supposedly inert gold components in autoclaves are reversibly oxidized by Cull (10) and it is likely that mixed oxine and hydroxy complexes of Fell contribute considerably to the gross under-estimation (by a factor of up to 10 ) of magnetite solubility in oxine (12,14). 

Some recent developments in the research of the structure and dynamics of solvated ions are discussed. The solvate structure of lithium ion in dimethyl formamide and preliminary results on the structure of sodium chloride aqueous solutions under high pressures are presented to demonstrate the capabilities of the traditional X-ray diffiraction method at new conditions. Perspectives of solution chemistry studies by combined methods as e.g. diffraction results with reverse Monte Carlo simulations, are also shown. 

Current Radiopharmaceutical Synthesis. The aqueous chemistry of technetium is dominated by the oxidizing power of soluble TcO , and the thermodynamic stability of insoluble TcOa. All technetium-99m radiopharmaceuticals, except pertechnetate itself, are prepared by the aqueous reduction of pertechnetate in the presence of a potential ligand to prevent Tc02 deposition (2). The most commonly employed reductant is stannous chloride, although many other reductants can, and have, been used (1,2). 

This notion of a reactive electrode is used much more widely In modern science. For instance it can be found in phase transfer chemistry or in the study of liquid-liquid interfaces. Figure 2.7 represents the phase transfer reaction between a potassium chloride aqueous solution and a solution of a crown-ether (denoted by L) in an organic solvent . ... 

The apparent rationale for study of the metallocene dihalides was that the cis geometry, Figure 6.4, was reminiscent of that of cisplatin, with a c chloride separation of 3.470 A for Ti, for example, in contrast to that in cisplatin, 3.349 A [102]. However, it is clear from studies of the hydrolysis of the cyclopentadienyl complexes that the aqueous chemistry is very different from that of platinum and no structural analogies should be drawn. In general, the complexes inhibit Ehrlich ascites tumours and solid growths of this tumour, are active in Lewis Lung, but are only very... 

An interesting feature is the observed adsorption sequence of Rf followed by Zr and Hf on the anion-exchange resin. This adsorption order reflects the strength of the chloride complex formation as Rf > Zr > Hf. The present result, however, contradicts the prediction with the relativistic molecular density-functional calculations by Pershina et al. where the sequence of the chloride complex formation is expected to be Zr > Hf > Rf [46] see Aqueous Chemistry of the Transactinides . 

Much of the aqueous chemistry is dominated by the existence of an equilibrium between mustard and a cyclic sulphonium ion (Figure 3). Hydrolysis is a result of hydroxide ion attack on a carbon atom of the three-membered sulphonium ring. The formation of the sulphonium ion is reversible and rate determining in the pH range 7-9. As might be expected, the rate of hydrolysis is inhibited by chloride ion and an increase in ionic... 

General Reaction Chemistry of Sulfonic Acids. Sulfonic acids may be used to produce sulfonic acid esters, which are derived from epoxides, olefins, alkynes, aHenes, and ketenes, as shown in Figure 1 (10). Sulfonic acids may be converted to sulfonamides via reaction with an amine in the presence of phosphoms oxychloride [10025-87-3] POCl (H)- Because sulfonic acids are generally not converted directiy to sulfonamides, the reaction most likely involves a sulfonyl chloride intermediate. Phosphoms pentachlotide [10026-13-8] and phosphoms pentabromide [7789-69-7] can be used to convert sulfonic acids to the corresponding sulfonyl haUdes (12,13). The conversion may also be accompHshed by continuous electrolysis of thiols or disulfides in the presence of aqueous HCl [7647-01-0] (14) or by direct sulfonation with chlorosulfuric acid. Sulfonyl fluorides are typically prepared by direct sulfonation with fluorosulfutic acid [7789-21-17, or by reaction of the sulfonic acid or sulfonate with fluorosulfutic acid. Halogenation of sulfonic acids, which avoids production of a sulfonyl haUde, can be achieved under oxidative halogenation conditions (15). 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenyiarsonium chloride in an organic solvent. Titanium(IV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenyiarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates deterrnined spectrophotometricaHy. Cobalt, palladium, tungsten, niobium, and molybdenum have been deterrnined in a similar manner. In addition to their use for the deterrnination of metals, anions such as perchlorate and perrhenate have been deterrnined as arsonium salts. Tetraphenyiarsonium permanganate is the only known insoluble salt of this anion. 

Aside from their extensive use in metaHacarborane chemistry, the dicarboUide anions are important intermediates in the synthesis of other carborane compounds. For example, aqueous ferric chloride oxidation of the 1 anion results in the 10-vertex cage nido- b ()-(Z, 2 (H8) and the... 

Chlorine dioxide gas is a strong oxidizer. The standard reversible potential is determined by the specific reaction chemistry. The standard potential for gaseous CIO2 in aqueous solution reactions where a chloride ion is the product is —1.511 V, but the potential can vary as a function of pH and concentration (26) ... 

In the meantime, we believe that the best prediction of the toxicity of an ionic liquid of type [cation] [anion] can be derived from the often well known toxicity data for the salts [cation]Cl and Na[anion]. Since almost all chemistry in nature takes place in aqueous media, the ions of the ionic liquid can be assumed to be present in dissociated form. Therefore, a reliable prediction of ionic liquids HSE data should be possible from a combination of the loiown effects of the alkali metal and chloride salts. Already from these, very preliminary, studies, it is clear that HSE considerations will be an important criterion in selection and exclusion of specific ionic liquid candidates for future large-scale, technical applications. 

Molten salt extraction residues are processed to recover plutonium by an aqueous precipitation process. The residues are dissolved in dilute HC1, the actinides are precipitated with potassium carbonate, and the precipitate redissolved in nitric acid (7M) to convert from a chloride to a nitrate system. The plutonium is then recovered from the 7M HNO3 by anion exchange and the effluent sent to waste or americium recovery. We are studying actinide (III) carbonate chemistry and looking at new... 

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