Preparation of Chlorides

In chlorination, the metal values in the ore or the concentrate are recovered by converting them into chlorides. Chlorination generally refers to a process in which metal chlorides are obtained by dry methods. There are two major types of chlorination. In one type, the metal chlorides produced are nonvolatile and are recovered from the reaction mixture as molten 

All metals, except those belonging to the platinum group, form chlorides and the free energy change for the reaction (referred to as reaction (1)) 

The standard free energy change for this reaction is generally positive at all temperatures because oxides are invariably stabler than chlorides. An exception to this rule occurs in the case of copper because cupric chloride is more stable than cupric oxide. At 500 °C, the standard free energy change (AG°) for the reaction 

The standard free energy associated with the reduction-chlorination reaction 

In this, to the free energy change for the reaction involving the interaction of chlorine and the metal oxide, is added the large value of the free energy of formation of carbon dioxide from its constituent elements. 

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Uses In preparation of chloride emulsions salting papers before sensitizing and before toning in hypo alum toning formulas, also acts as a weak restrainer. 

In all these protocols, chemoselective amidation of vanillamine with NMA was achieved in satisfactory yield (about 80 %) by activation of the add to its corresponding chloride, followed by condensation with free vanillamine. Free vanillamine is much less stable than its corresponding chloride, and, owing to its polarity, it is difficult to extrad quantitatively from water solution, with loss of about 20 % of the product routinely observed in the desalification step [59]. Furthermore, the preparation of chlorides from polyunsaturated fatty acids is not trivial, and therefore alternative coupling protocols were investigated in a series of systematic studies dedicated to the structure-adivity relationships of capsaicinoids. 

For the preparation of chlorides or bromides, the diazonium salt is decomposed with a solution of cuprous chloride or bromide in the corresponding halogen acid (Sandmeyer reaction). It is possible to prepare the aryl bromide from the diazonium chloride or sulfate. A variation Involves the use of copper powder and a mineral acid for the decomposition step (Gattermann reaction). Both procedures are illustrated by the syntheses of the isomeric bromotoluenes and chlorotoluenes. The usual conditions of the Sandmeyer reaction fail in the preparation of the chloro- and bromo-phenanthrenes. However, these compounds can be successfully obtained by the interaction of the diazonium compound with mercuric and potassium halides (Schwechten procedure). Another procedure for formation of aryl bromides involves treatment of the amine hydrobromide with nitrogen trioxide in the presence of excess 40% hydro-bromic acid. The Intermediate diazonium perbromide is then decomposed by heat. ... 

Sorum, S. H. (1928) Preparation of chloride free, colloidal Fe203 from FeCls. J. Amer. Chem. Soc. 1263-1267. 

SOCb is used extensively in the preparation of chlorides (Scheme 2) although this reaction can give a variety of by-products. Yields are typically in the 70-90% range. In the absence of base retention of configuration is the rule (Scheme 3). lliis has been explained by an 5n1 mechanism or by participation of the solvent. The fact that the secondary chlorosulfite (1) gives, on heating, the tertiary chloride (3), indicates that an intramolecular single step mechanism is ruled out and an ion pair (2) may be involved (Scheme 4). If the reaction is done in the presence of one equivalent of pyridine, inversion (Sn2) is likely to occur. ... 

For the preparation of chlorides of carboxylic and sulfonic acids which do not react with thionyl chloride alone, see Dimethylformamide-Thionyl chloride. 

The preparation of chlorides by decarboxylation of carboxylic acids with lead tetraacetate and N-chlorosuccinimide as the chlorine donor in a 5 1 mixture of DM F and glacial acetic acid has been reported [71 a]. The reaction has been applied particularly often to the preparation of secondary and tertiary chlorides when the classic Hunsdiecker reaction gives low yields (Scheme 13.50) [71b]. This reaction proceeds by a radical pafhway. 

Somm, C.H., The preparation of chloride free colloidal ferric oxide from ferric chloride, J. Am. Chem. Soc., 50, 1263, 1928. 

Thionyl chloride is used extensively for the preparation of chlorides. In the absence of base, retention of configuration is always observed. This has been rationalized by an SNi mechanism or by participation of the solvent46. Thionyl chloride in hexamethylphosphoric triamide46 or chloroform47 gives clean SN2 chlorinations of chiral secondary alcohols. Allylic silyl ethers are chlorinated with thionyl chloride in an SN2 reaction48. 

For information on the mechanism the original literature917 should be consulted. The preparation of chlorides by SOCl2 with addition of pyridine918 or... 

Fig. 147. Droppii funnel apparatus for preparation of chloride dioxide.

The mild reaction conditions employed enables the preparation of chlorides without disrupting chiral or other sensitive functionality. The use of hexane has been found particularly suitable for microscale preparation of high purity Mosher s acid chloride as it enables residual DMFCl to be filtered from solution (eq 2). ... 

Fischer, therefore, as Curtius with his benzoyl in the beginning of his studies, was able to perform coupling only at the carboxyl group, and for this purpose, he worked out the preparation of chlorides by reaction of the acids with thionyl chloride. Since, however, the reaction, by no means, runs smoothly Fischer switched to PCI5 in the unusual solvent acetyl chloride. He showed that in this system, finely powdered free mono amino acids and even small peptides can also be transformed to their chloride hydrochlorides [9]. 

In Fig. 9.13, the heat treatments are necessary to improve the efficiency of the sulphation step. The latter can be engineered in several alternative types of plant. Alternatives are available for the subsequent steps to pure oxide, but usually based upon precipitation and crystallization, as is the one shown in Fig. 9.13. The precipitation of beryllium hydroxide by boiling an alkaline solution of sodium beryllate, is a particularly valuable purification step, and is also used in Fig. 9.14. Chlorination of oxide mixed with carbon is a standard type of operation as used for the preparation of chloride intermediates of other metals. Molten salt electrolysis is one of the two alternative commercial routes to pure beryllium metal, the other being shown in Fig. 9.14. 

Preparation of chloride-free HQO by electrodialysis, distillation, or solvent extraction before conversion to NaQO with alkali [22-27]... 

A useful method for preparation of chlorides from alcohols is based on the... 

Thionyl chloride, SOCI2, is frequently used for preparation of chlorides from alcohols. There are two mechanisms by which thionyl chloride reacts with alcohols. In nucleophilic solvents such as dioxane, net retention of configuration is possible because of participation by the solvent. In the absence of such solvents ne>... 

Ureides can be obtained by reacting urea with acid chlorides or with their esters (for the preparation of chlorides see p. 255 for the preparation of esters see p. 252). Ureides crystallize well and are suitable mainly for the identification of higher fatty acids. 

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