Halogen atoms, combination

The colloidal metallic silver formed in this way is opaque (it would appear black in reflected or transmitted light). The halogen atoms combine with an organic substrate mixed with the silver halide crystals to produce bromides. 

EhmmaUon of any combination of fluorme, chlorme, bromme, or lodme is also possible when the halogen atoms to be removed are on the same carbon atom The... 

The oxidation number of every halogen atom in its compounds is - 1 except for a chlorine, bromine, or iodine atom combined with oxygen or a halogen atom higher in the periodic table. For example, the chlorine atoms in each of the following compounds have oxidation numbers of -1 ... 

Atom Transfer Atom Transfer (AT) takes place typically in the case of d7 complexes, which abstract the halogen atom from RX. The radical formed combines then with a second metal [193, 194]. A classical example of this mechanism is the hydrodehalogenation with cyanocobaltates(II) (see Section 18.2.1) [8, 9], but an analogous pathway was suggested recently for the Co(II) corrin-catalyzed dechlorination of CC14 in the presence of S2 /cysteine as reductant (Eqs. (11)—(12))... 

CsCl HgCl2=3 1, 2 1, 1 1, 2 3, 1 2, and 1 5 and five caesium antimonious fluorides where CsF SbF3=l 1, 3 4, 4 7, 1 2, and 1 3. According to I. Remsen s rale (1889) When a halide of any element combines with a halide of an alkali metal to form a double salt, the number of molecules of the alkali salt which are added to one molecule of the other halide is never greater, and is generally less than the number of halogen atoms contained in the latter—for instance, in the double fluoride of sodium and aluminium, where the negative halide has three fluorine atoms, no more than three molecules of sodium fluoride will be found united with one of aluminium fluoride. 

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... 

Combinations of metal halides (e. g. FeCl3, A1C13) with compounds containing an active halogen atom (e. g. a-chloro-dimethyl ether, benzyl chloride, 2,3-dichloro THF). 

For fluorine, the only n interaction possible involves the filled p orbitals on fluorine overlapping with suitable empty orbitals on the combining atom. The other halogens can n bond in this way but there is also the possibility of % bonding in the opposite sense, with filled orbitals on the central atom overlapping with empty d orbitals on the halogen atom. 

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