Interhalogens formation

At(0) reacts with halogens X2 to produce interhalogen species AtX, which can be extracted into CCI4, whereas halide ions X yield polyhalide ions AtX2 which are not extracted by CCLt but can be extracted into Pr O. The equilibrium formation constants of the various trihalide ions are intercompared in Table 17.28. 

The interhalogen IFT can be made only by indirect routes. For example, xenon difluoride gas can react with iodine gas to produce 1FV and xenon gas. In one experiment xenon difluoride is introduced into a rigid container until a pressure of 3.6 atm is reached. Iodine vapor is then introduced until the total pressure is 7.2 atm. Reaction is then allowed to proceed at constant temperature until completion by solidifying the IF as it is produced. The final pressure in the flask due to the xenon and excess iodine vapor is 6.0 atm. (a) What is the formula of the mterhalogen (b) Write the chemical equation for its formation. 

The reactivity of iodine has been investigated at liquid-liquid-electrode triple-phase boundary systems. Scholz et al. [162] demonstrated that the reduction of iodine dissolved in a nitrobenzene microdroplet triggered the transfer of cations from the aqueous into the organic solution phase (Scheme 6). In addition, the formation of IzCl" interhalogen anions in the organic phase was discovered and shown to be the key to the overall process. 

In addition to the polyhalide ions discussed previously, which were all anionic, there are comparable cationic species known, although they have been studied considerably less. Many pure interhalogen compounds arc thought to undergo autoionization (see Chapter 10) with the formation of appropriate cationic species ... 

In general, addition of more polar interhalogen compounds (ICI, IF, BrF, ClF) to fluoroolefins proceeds as an ionic process, starting with attack of halogen bearing positive charge on the C=C bond and formation of a cyclic halonium cation (Eq. 2) [10,18]. 

Formation of these anionic species is not limited to species that contain only one halogen, and some interhalogen anions are also formed ... 

Reactions of the mercurial with halogens or interhalogens lead to the formation of a series of pentafluorosulfanyl AMialo(trifluoromethyl) amines, SF5N(X)CF3 (X = F, Br, Cl, I) (210). 

Good evidence for the formation of charge-transfer complexes comes from the isolation and structure determination of solids. Chlorine and Br2, as well as the interhalogens IBr and Id, have been found to behave similarly to iodine. Some examples of crystal structures are ... 

Cation formation is not restricted, as normally observed, to association with metallic species. It can also occm among nonmetals and even the most typical ones such as halogens or interhalogens, which are usually more noted for halide and polyhalide anion formation. 

Ion of 1 — charge Neutral dimeric species Hydrohalic acid Formation of interhalogen compounds... 

Halide ions often react with molecules of halogens or interhalogens and form polyhalide ions. Iodine is only slightly soluble in water. Its solubility is greatly increased if same iodide ions are present in the solution. The increase in solubility is due to the formation of polyhalide ion, in this case triiodide ion I3 This is stable both in aqueous solution and in ionic crystals. 

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