Other Halides

The other halides dissociate at lower temperatures and, if put into water, all are decomposed, the proton transferring to water which is a better electron pair donor ... 

Many ionic halides dissolve in water to give hydrated ions. The solubility of a given halide depends on several factors, and generalisations are difficult. Ionic fluorides, however, often differ from other halides in solubility. For example, calcium fluoride is insoluble but the other halides of calcium are highly soluble silver fluoride. AgF, is very soluble but the other silver halides are insoluble. 

The process whereby aldehydes are produced from arylmethyl (also alkyl and other) halides by the action of hexamine is known as the Sommelet reaction. The reaction is essentially the conversion of an amine into an aldehyde the hexamine serves the dual role of converting the halide into the amine and the amine into the aldehyde, but its function is different in the two steps. When starting from a halide, the reaction proceeds in three stages —... 

Halide derivatives may be fluorides, chlorides, or bromides. Fluorides are best prepared by the reaction of hydroxy groups with (diethylamino)sulfur trilluoride ( DAST M. Sharma, 1977) or of glycosyl thioethers with DAST/NBS (K.C. Nicolaou, 1990 B). The other halides are usually only introduced at the glycosidic position, where treatment with hydrogen chloride... 

Other Halides. TaBr /-/y and Tal [14693-81-3] are well known but do not find industrial appHcation. An exceUent overview of the... 

Reaction with Other Halides. Bromide ion is oxidi2ed by chlorine to bromine. This is the basic reaction in the production of bromine from seawater, brines, or bitterns. 

The seven known sulfur fluorides are quite different from the other halides of sulfur in their stability, reactivity and to some extent even in their stoichiometries it is therefore convenient to... 

A detailed discussion of individual halides is given under the chemistry of each particular element. This section deals with more general aspects of the halides as a class of compound and will consider, in turn, general preparative routes, structure and bonding. For reasons outlined on p. 805, fluorides tend to differ from the other halides either in their method of synthesis, their structure or their bond-type. For example, the fluoride ion is the smallest and least polarizable of all anions and fluorides frequently adopt 3D ionic structures typical of oxides. By contrast, chlorides, bromides and iodides are larger and more polarizable and frequently adopt mutually similar layer-lattices or chain structures (cf. sulfides). Numerous examples of this dichotomy can be found in other chapters and in several general references.Because of this it is convenient to discuss fluorides as a group first, and then the other halides. 

Apart from XeF, which is the light-emitting species in certain Xe/F2 lasers, there is no evidence for the existence of any odd-valent fluorides. Reports of XeFg have not been confirmed. Of the other halides, XeCl2, XeBr2 and XeCl4 have been detected by Mossbauer spectroscopy as products of the -decay of their... 

This oxidation state is sparse in the case of Mn but is important in the pharmaceutical applications of Tc, and an extensive chemistry has been developed. Some fluoro complexes of Tc and Re such as the salts of [MFe] are known, but oxo compounds predominate and, in [MOCls] and [MOX4] (X = Cl, Br, I) for instance, other halides are also able to coordinate. [MOX4] is square pyramidal with apical M=0 and the moiety is reminiscent... 

M(N03)4] anions containing the unusual unidentate niirato ion are also known. Fluoro complexes are even less prevalent, the preference of these cations being for the other halides, cyanide, N- and heavy atom-donor ligands. 

The other halides of Zn and Cd are in general hygroscopic and very soluble in water ( 400g per lOOcm for ZnXa and 100g per lOOcm for CdXa). This is at least partly because of the formation of complex ions in solution, and the anhydous forms are best prepared by... 

The coordination chemistry of Zn" and Cd", although much less extensive than for preceding transition metals, is still appreciable. Neither element forms stable fluoro complexes but, with the other halides, they form the complex anions [MX3] and [MX4] , those of Cd" being moderately stable in aqueous solution. "" By using the large cation [Co(NH3)6] + it is also possible to isolate the trigonal bipyramidal [CdCls] "... 

Nucleophilic substitution of the halogen atom of halogenomethylisoxazoles proceeds readily this reaction does not differ essentially from that of benzyl halides. One should note the successful hydrolysis of 4-chloromethyl- and 4-(chlorobenzyl)-isoxazoles by freshly precipitated lead oxide, a reagent seldom used in organic chemistry. Other halides, ethers, and esters of the isoxazole series have been obtained from 3- and 4-halogenomethylisoxazoles, and 3-chloro-methylisoxazole has been reported in the Arbuzov rearrangement. Panizzi has used dichloromethylisoxazole derivatives to synthesize isoxazole-3- and isoxazole-5-aldehydes/ ... 

Austenitic stainless steels Chloride (and other halide) ion Polythionic acids High-temperature water Hydrogen sulfide (aqueous)... 

The fracture mode of stress-corrosion cracks in austenitic stainless steels can be transgranular, intergranular or a mixture of both. One of the earliest environments found to cause problems was solutions containing chlorides or other halides and the data due to Copson (Fig. 8.30) is very informative. The test solution for that data was magnesium chloride at 154°C the alloys contained 18-20alloy with a composition of approximately 18Cr-8Ni has the least resistance to cracking in this environment. 

Although the viscosity B-coefficients for the fluorides are not known, we see. that the value for the ionic entropy of F" listed in Table 45 is — 2.3 + 2, very different from the value +13.5 for Cl". The value for F- is, in fact, very near the value —2.49 for (OH)-. We have then the very interesting question, whether the activities of the fluorides will fall in line with the other halides. In structure the ion F" certainly resembles Cl" and the other halide ions but according to the tentative scheme proposed above, we should perhaps focus attention on the solvent in the co-sphere of each ion. In this case we should expect to obtain for the fluorides a family of curves similar to that of the hydroxides, in contrast to that of the chlorides. The activities are known as a function of concentration for NaF and KF only. It is found that the curve for NaF lies below that of KF—that is to say, the order is the same as that of NaOH and KOII, in contrast to that of NaCl and KC1. 

The bromide (5) failed to couple with dialkoxypyrimidines, even at elevated temperatures the failure is probably because of steric conditions imposed by the axially oriented C-4 p-nitrobenzoyloxyl group (see structure 5) this same group in the other halides (la, lb, 2a, 2b, 4a, and 4b) discussed in the foregoing is an equatorial substituent. Accordingly, the preparation of a differently constituted halide of 2-deoxy-D-Zt/xo-hexose is being investigated for the synthesis of pyrimidine nucleosides. 

Determination of iodide as silver iodide Discussion. This anion is usually determined by precipitation as silver iodide, Agl. Silver iodide is the least soluble of the silver halides 1 litre of water dissolves 0.0035 mg at 21 °C. Co-precipitation and similar errors are more likely to occur with iodide than with the other halides. 

Some fluorine-ion conductors exhibit high ionic conductivities, even at room temperature [4], which are not equaled by other halide-ion conductors. However, there is a lack of known electrode materials. Further research on this topic is very worthwhile. 

Other halides can be introduced by metathesis. Figure 2.55 summarizes some of the complexes isolable with dimethylphenylphosphine, similar in general to the corresponding iridium complexes (section 2.13.3), including the photochemical isomerization of the mer-isomer. 

This synthesis is possible with other halide ligands... 

This synthesis is of course analogous to those for the bisammine complexes. It can be applied to substituted pyridines and other halides (Br, I, NCS) [81]. 

Reaction of the diphosphines Ph2P(CH2) PPh2 (n = 1-3) with MCl2(PhCN)2 affords 1 1 m-complexes (Figure 3.46) [102]. (Note the use of the labile PhCN adducts if the MCl salts are used, Magnus type compounds M(P-P)2+MCl4- are formed.) Similar complexes are formed with other halides for the thiocyanates see section 3.8.6. The structures of the palladium complexes have been determined (Table 3.10) with square coordination only achieved for n = 3 with the formation of a six-membered metal-chelate ring. 

Because the fluoride ion is so small, the lattice enthalpies of its ionic compounds tend to be high (see Table 6.6). As a result, fluorides are less soluble than other halides. This difference in solubility is one of the reasons why the oceans are salty with chlorides rather than fluorides, even though fluorine is more abundant than chlorine in the Earth s crust. Chlorides are more readily dissolved and washed out to sea. There are some exceptions to this trend in solubilities, including AgF, which is soluble the other silver halides are insoluble. The exception arises because the covalent character of the silver halides increases from AgCl to Agl as the anion becomes larger and more polarizable. Silver fluoride, which contains the small and almost unpolarizable fluoride ion, is freely soluble in water because it is predominantly ionic. 

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