POLY-HALIDES

When iodine is dissolved in hydriodic acid or a soln. of a metallic iodide, there is much evidence of chemical combination, with the formation of a periodide. A. Baudrimont objected to the polyiodide hypothesis of the increased solubility of iodine in soln. of potassium iodide, because he found that an extraction with carbon disulphide removed the iodine from the soln. but S. M. Jorgensen showed that this solvent failed to remove the iodine from an alcoholic soln. of potassium iodide and iodine in the proportion KI I2, and an alcoholic soln. of potassium iodide decolorized a soln. of iodine in carbon disulphide. The hypothesis seemed more probable when, in 1877, G. S. Johnson isolated cubic crystals of a substance with the empirical formula KI3 by the slow evaporation of an aqueous-alcoholic soln. of iodine and potassium iodide over sulphuric acid. There is also evidence of the formation of analogous compounds with the other halides. The perhalides or poly halides—usually polyiodides—are products of the additive combination of the metal halides, or the halides of other radicles with the halogen, so. that the positive acidic radicle consists of several halogen atoms. The polyiodides have been investigated more than the other polyhalides. The additive products have often a definite physical form, and definite physical properties. J. J. Berzelius appears to have made the first polyiodide—which he called ammonium bin-iodide A. Geuther called these compounds poly-iodides and S. M. Jorgensen, super-iodides. They have been classified 1 as... 

A number of other substances, for example CC14, CCl3Br, and several other alkyl poly halides, aldehydes, and thiols, add successfully to olefins.150 Addition of Cl2, frequently looked upon as ionic, often occurs as a radical chain reaction, particularly in nonpolar solvents and in the presence of light or peroxides.151... 

Furthermore, Seddon et al. reported that the poly-halide salts, such as [EMIM][IBr2] or [EMIM][Is], have a high refractive index of 1.6 or more, as shown in Table 3.7 [67]. The high refractive indices of the lanthanide salts and the heavy halogens and their trihalide salts are well predictable from their polarizabilities, which in turn are well understood on the basis of periodic table trends atoms/ions with partly filled 4f, 5d etc. shells tend to be quite polarizable and hence have high refractive indices. 

F. Ephraim found that if T denotes the absolute temp, at which the vap. press, of the liberated halogen is equal to one atm., then for corresponding pairs of the caesium and rubidium poly halides, r(>s/rjRj=lT2 and, if v denotes the at. vol., T is the same for the two members of each series. Given the dissociation temp, of the caesium compound, it is possible to predict the stability of the analogous rubidium compound. F. Ephraim extended the rule to the potassium compounds when the corresponding rubidium compounds are known. 

Haloalkylations have also been carried out with branched, unsymmetrical simple di- and poly-halides, straight-chain, unsymmetrical simple di- and poly-halides, and mixed di- and poly-halides. Schmerling et a/.have studied the Friedel-Crafts reactions of benzene with l,3-dichloro-3-methylbutane in the presence of AlCb and obtained a 28-29% yield of l-chloro-3-methyl-3-phenylbutane (equation 81). 

Halogen oxidation of planar complexes, particularly of the nickel triads that contain bidentate glyoximes or macrocyclic ligands, such as, phthalocyanines, substituted porphyrins, or tetraazaannulenes, leads to highly conducting substances that may possess chains of metal atoms as well as chains of poly halides E... 

The list of existing polyhalogen anions is rather impressive since, except for fluorine, nearly every combination of halogens is possible. Fluorine does not readily form polyhalogen complexes, and when it does, both the methods of preparation and the properties of the resulting complexes lie somewhat apart from the other poly halides. This discussion is limited primarily to the complexes of chlorine, bromine, and iodine. 

The stability of the solid polyhalide depends on numerous factors, among them the size of the cation, the size and the nature of the polyhalide ion, and the chemical resistance of the compound to atmospheric moisture. The most stable salts are formed when the ionic sizes of the cation and the anion are similar. In the alkali metal series the stability of the polyhalides decreases in the order Cs > Rb > NH4 > K > Na, which corresponds to the order of decrease in cationic size. Not enough work has, as yet, been done on the substituted onium poly halides to allow any convincing generalizations. 

Essentially all the simple geminal di- or poly halides studied have been derivatives of methane. Reaction of diiodomethane (25,103) with triethyl phosphite proceeds normally, to furnish tetraethyl methanedi-phosphonate and iodomethanephosphonate. However, the reaction between carbon tetrachloride and trialkyl phosphite, first investigated by Kamai and Egorova (156,181), is catalyzed by peroxides or ultraviolet light, and accordingly it has been formulated by Kamai and Kharrasova (157) as a radical-chain process. 

TABLE V. ORGANIC DERIVATIVES OF HALIDES B) Dihalides and poly halides (non-aromatic)... 

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