Iodine solubility, organic solvents

Lithium Iodide. Lithium iodide [10377-51 -2/, Lil, is the most difficult lithium halide to prepare and has few appHcations. Aqueous solutions of the salt can be prepared by carehil neutralization of hydroiodic acid with lithium carbonate or lithium hydroxide. Concentration of the aqueous solution leads successively to the trihydrate [7790-22-9] dihydrate [17023-25-5] and monohydrate [17023-24 ] which melt congmendy at 75, 79, and 130°C, respectively. The anhydrous salt can be obtained by carehil removal of water under vacuum, but because of the strong tendency to oxidize and eliminate iodine which occurs on heating the salt ia air, it is often prepared from reactions of lithium metal or lithium hydride with iodine ia organic solvents. The salt is extremely soluble ia water (62.6 wt % at 25°C) (59) and the solutions have extremely low vapor pressures (60). Lithium iodide is used as an electrolyte ia selected lithium battery appHcations, where it is formed in situ from reaction of lithium metal with iodine. It can also be a component of low melting molten salts and as a catalyst ia aldol condensations. 

Like bromine, iodine is soluble in organic solvents, for example chloroform, which can be used to extract it from an aqueous solution. The iodine imparts a characteristic purple colour to the organic layer this is used as a test for iodine (p. 349). NB Brown solutions are formed when iodine dissolves in ether, alcohol, and acetone. In chloroform and benzene a purple solution is formed, whilst a violet solution is produced in carbon disulphide and some hydrocarbons. These colours arise due to charge transfer (p. 60) to and from the iodine and the solvent organic molecules. 

Magnesium iodide is soluble in alcohols and many other organic solvents, and forms numerous addition compounds with alcohols, ethers, aldehydes, esters, and amines. One example is magnesium iodide dietherate [29964-67-8], Mgl2 prepared by gradual addition of iodine to a... 

A solid solution of starch in urea may also be employed. Reflux 1 g of soluble starch and 19 g of urea with xylene. At the boiling point of the organic solvent the urea melts with little decomposition, and the starch dissolves in the molten urea. Allow to cool, then remove the solid mass and powder it store the product in a stoppered bottle. A few milligrams of this solid added to an aqueous solution containing iodine then behaves like the usual starch indicator. 

When iodine dissolves in organic solvents, it produces solutions having a variety of colors. These colors arise from the different interactions between the I2 molecules and the solvent (Fig. 15.21). The element is only slightly soluble in water, unless I ions are present, in which case the soluble, brown triiodide ion, I,, is formed. Iodine itself has few direct uses but dissolved in alcohol, it is familiar as a mild oxidizing antiseptic. Because it is an essential trace element for living systems but scarce in inland areas, iodides are added to table salt (sold as iodized salt ) in order to prevent an iodine deficiency. 

Tracer studies of the chemical properties showed that astatine was soluble in organic solvents, could be reduced to the —1 state, and had at least two positive oxidation states. These studies were made on solutions of 10-11 to KL15 molar astatine (29). The similarity between astatine and iodine was found to be less close than that between technetium and rhenium or that between promethium and the other rare earths (30). 

The solubility of the halogens in organic solvents.—L. Bruner33 has measured the solubility of iodine in mixtures of ethyl alcohol and water at 15° ... 

Compound 48 is described as a hypervalent iodine compound possessing the distinctive advantages of being air-stable, non-explosive and soluble in common organic solvents.112... 

Dimethyliodoarsine (m.p. ca. —35° b.p. 154 to 160°) is a yellow oil of penetrating odor, soluble in organic solvents but insoluble in water. It is volatile with steam and inflames when heated in air with the liberation of iodine vapors. Dimethyliodoarsine is decomposed by both nitric and sulfuric acids with the separation of iodine. 

The iodine gives a reddish-brown color to water. However, since iodine is more soluble in organic solvents, such as hexane, C6H14, the iodine dissolves in the organic solvent. The organic solvent separates from the water, and the iodine colors the organic solvent violet. 

These compounds are soluble in carbon disulphide, from which they may be obtained as orange or yellow crystals. They are only slightly soluble in other organic solvents such as benzene, chloroform, etc. They can be burnt in air, giving oxides of phosphorus, sulphur and iodine. They are decomposed by warm water or moist air, giving first phosphoric and hydriodie acids, then phosphoric acid and hydrogen sulphide.4... 

Hypervalent iodine compounds, such as l-(difluoroiodo)-4-methylbcnzcnc or l-(difluoroiodo)-4-methoxybenzene, can serve as oxidant and simultaneously as the source of fluoride ions. They are used for fluorodesulfurization reactions under mild conditions.229 230 The reagents arc crystalline and soluble in organic solvents. 

---