Iodinated substances, preparation with

The free iodine can readily he washed out, but CaCl2 can be removed only incompletely because all the solvents for this substance react with silicon chloride. The reaction will take place quantitatively only if the starting CaSi2 has been finely ground under inert gas or in a solvent. Grinding in air leads to partial oxidation and the reaction remains incomplete. Silicon monochloride prepared in this way is a yellow scaly product whose analysis indicates the exact 1 1 silicon to chlorine ratio. The quantity of hydrogen liberated in alkaline medium is also consistent with the three Si-Si bonds per silicon atom required for the layer structure. 

Trichloromethanesulfenyl chloride (5) is a yellow oily substance, volatile with steam, having a very unpleasant odour, with a boiling point of 146-149°C. It is prepared by the chlorination of carbon disulfide below 30°C in the presence of iodine as catalyst (Klason, 1887) ... 

The main role of the human thyroid gland is production of thyroid hormones (iodinated amino acids), essential for adequate growth, development, and energy metaboHsm (1 6). Thyroid underfunction is an occurrence that can be treated successfully with thyroid preparations. In addition, the thyroid secretes calcitonin (also known as thyrocalcitonin), a polypeptide that lowers excessively high calcium blood levels. Thyroid hyperfunction, another important clinical entity, can be corrected by treatment with a variety of substances known as antithyroid dmgs. 

The treatment of unsaturated substances with halogen leads to addition to these molecules. This is true not only of bromine and chlorine vapor but also of the less reactive iodine. Substitution also occurs in the presence of light. Examples of such halogenations are listed in Table 12. Figure 32 illustrates the characterization of fluorescein in a bubble bath preparation. Bromination of the fluorescein in the start zone yields eosin. 

Direct bromination readily yields the 6-bromo derivative (111), just as with uracil. Analogous chlorination and iodination requires the presence of alkalies and even then proceeds in low yield. The 6-chloro derivative (113) was also obtained by partial hydrolysis of the postulated 3,5,6-trichloro-l,2,4-triazine (e.g.. Section II,B,6). The 6-bromo derivative (5-bromo-6-azauracil) served as the starting substance for several other derivatives. It was converted to the amino derivative (114) by ammonium acetate which, by means of sodium nitrite in hydrochloric acid, yielded a mixture of 6-chloro and 6-hydroxy derivatives. A modified Schiemann reaction was not suitable for preparing the 6-fluoro derivative. The 6-hydroxy derivative (115) (an isomer of cyanuric acid and the most acidic substance of this group, pKa — 2.95) was more conveniently prepared by alkaline hydrolysis of the 6-amino derivative. Further the bromo derivative was reacted with ethanolamine to prepare the 6-(2-hydroxyethyl) derivative however, this could not be converted to the corresponding 2-chloroethyl derivative. Similarly, the dimethylamino, morpholino, and hydrazino derivatives were prepared from the 6-bromo com-pound. ... 

If the mixture components are not colored, any of a number of techniques designed to make the spots visible may be employed. These include iodine staining, in which iodine vapor is allowed to contact the plate. Iodine will absorb on most spots, rendering them visible. Alternatively, a fluorescent substance may be added to the stationary phase prior to the separation (available with commercially prepared plates), such that the spots, viewed under an ultraviolet light, will be visible because they do not fluoresce while the stationary phase surrounding the spots does. 

In this titration method an excess of iodine solution is added to the solution of the substance and thus, the latter gets oxidized quantitatively. The excess of iodine is subsequently back titrated with sodium thiosulphate using freshly prepared starch solution as indicator with an end-point from violet to colourless. 

Procedure Weigh accurately about 0.2 g of ethacrynic acid, dissolve in 40 ml of glacial acetic acid in a 250 ml iodine flask. Add to it 20 ml of 0.1 N bromine and 30.0 ml of hydrochloric acid, immediately place in position the moistened stopper to the ffask, mix the contents vigorously and allow it to stand in a dark place for 60 minutes (to complete the reaction with bromine). Add to it 100 ml of water and 20 ml of KI Solution and titrate immediately with 0.1 sodium thiosulphate, employing freshly prepared starch solution as an indicator towards the end of the titration. Repeat an operation without the pharmaceutical substance (blank titration) thus the difference between the titrations represents the amount of bromine required by the ethacrynic acid. Each ml of 0.1 N bromine is equivalent to 0.01516 g of C13H12C1204. 

The iodine atom in the monoiodide may be replaced by other groups and, by reaction with silver salts, for example, As(CF3)2CN (b.p. 89 5°) and As(CFg)2SCN (b.p. 116—118°) are readily prepared. Reaction of the monoiodide with mercury gives the cacodyl As2(CF3)4 (b.p. 106 to 107°), while with mercuric oxide the oxide As2(CF3)40 (b.p. 95—97°) is formed. The chemistry of these substances has not yet been studied in detail, but it is noteworthy that hydrolysis of the perfluorocacodyl gives both fluoroform and fluoride, which parallels the observations made on the diphosphine. 

As soon as he had read Balard s paper on bromine, Liebig examined the brine from Theodorshalle near Kreuznach and prepared nearly twenty grams of bromine. His experiments led him to conclude, as Balard had done, that it must be a simple substance (27). I know a chemist, said he, years later (referring to himself), who during a visit to Kreuznach occupied himself with the investigation of the saline mother liquors there he found iodine in them and observed that the iodine-starch, when left... 

Transfer the iodine trichloride from the flask into a weighed drawn out test tube. Cool the tube with dry ice and rapidly seal it wear eye protection ). Weigh the test tube with the substance and the remaining fragments of the tube. Calculate the yield in per cent. Write the equation of the reaction. Use the prepared iodine trichloride in the following syntheses. 

The Union of Two Elementary Substances.— The most obvious way in which to prepare a binary compound is by the union of the two constituent elements, though in many cases this is not the most practicable way. Sometimes, the elements are first prepared in pure form and are then combined in other cases, the preparation of the elements and their union is effected in one operation, as in the manufacture of calcium carbide and carborundum. In general, the more dissimilar the two elements the more likely they are to combine readily, but elements of the same general kind sometimes combine with ease, as is the case with chlorine and iodine, sulfur and phosphorus, or sodium and lead. 

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