Super-halogen atom

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... 

Photoheterolysis of benzylic chlorides [204] yielded results signifying that simple benzyl cations, such as cumyl and 1-phenylethyl cations, can exist in the solution as free ions radicals arising from a competing photohomolysis are also observed frequently. Haloalkyl-carbocations are studied by heterolysis of the corresponding dihalides in super acid media [205]. NMR chemical shifts are interpreted as evidence for an interaction between the vacant orbital of cationic center of the haloalkyl carbocations with a lone electron pair of the halogen atom. 3-chloro-l-methylcyclopentyl cation 73, thermally eliminates hydrogen chloride and yields l-methyl-2-cyclopentyl cation 74, a similar behavior reported for y-chloroalkyl carbocations [206] (Scheme 5). 

The super-halogen character of AI13 is a subject of debate. Bergeron and coworkers [9,18] have concluded that the super-halogen character is confirmed in their study of the reaction of Alj3 with HI. They propose that the experimental reaction outcomes are dominated by the pseudo-halide nature of Alfj a stable AI13I species forms in which the Al j framework is preserved even in the reactive environment of an I atom. Experiments [7] and calculations [19] indicate that the electron affinity of neutral AI13 is 3.4-3.6 eV. The I atom has a lower affinity, 3.06 eV, so Alfj is... 

The electronically excited rare gas atom is sometimes called a super-alkali because its ionization potential is so low. There are also super-halogens and not only super-alkalis (Herschbach, 1966 Bersohn, 1976). The super-halogen has a particularly high electronic affinity NO2, with an electron affinity of about 2.4 eV, is an example so is (CN)2. Excited states of organic molecules are used as effective electron donors. Complexes of transition metals in unusually high oxidation states are keen acceptors and vice versa for complexes where the metal is nominally neutral. 

On the basis of its electronic properties, which are close to those of a chlorine or a fluorine atom [70], the trifluoromethoxy group has been referred to as a super- [71] or a pseudo-halogen [72], The advantage of incorporating a trifluoromethoxy group into a molecule can be described in terms of its properties. The trifluoromethoxy group is... 

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