Halogenated Compounds Other Than Fluorinated

Chapter /7 Halogenated Compounds (Other Than Fluorinated Compounds)... 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

In ABj compounds where B is a halogen other than fluorine or a chalcogen (S, Se, Te), the A—B bond is considerably covalent and a different set of structures is encountered. Some of the important structures are shown in Fig. 1.8. 

The oxygen compounds of the halogens (other than fluorine) are very important substances. A few of them, such as potassium chlorate, have been mentioned in earlier chapters. The chemistry of these substances is complex, but it can be systematized and clarified by correlation with the electronic theory of valence. This is the reason that the treatment of these compounds was not included in Chapter 9 but was postponed to this place. Some aspects of the chemistry of the halogens themselves and of the hydrogen halides are also presented in this chapter. 

The halogens other than fluorine form stable compounds corresponding to nearly all values of the oxidation number from —1 to +7, as shown in the accompanying chart. 

No compound containing a halogen other than chlorine appears among the top 50 industrial chemicals, but fluorine nevertheless has considerable commercial value. Fluorine occurs as the mineral fluorite (CaF2) and is prevalent in phosphate-bearing rock. As already mentioned, HF produced from sulfiaric acid treatment of fluorite supplies some 70% of industrial HF the remainder comes as a by-product of phosphoric acid production. 

It is well established that hydrogen forms more than one covalenl binary compound with carbon. Fluorine behaves similarly. Thus, fluorine forms CFi. C>F4. CjFV,. C.rFx and many higher hontologs. as well as the definitely imerstiiial compound (CF) . The other halogens form some similar compounds, although 10 more limited extent, and various polyhalogen compounds have been prepared. They exhibit the maximum covalencv of four and are therefore inert to hydrolysis and most other low temperature chemical reactions. 

Considerably less work has been done on the kinetic aspects of the radiolysis of fluorine compounds than on other halogen compounds. With °Co y-radiation, perfluoromethane produces perfluoroethane , and perfluoroethane produces (refs. 351, 352) a mixture of perfluoromethane, -propane, -butane, -cyclopropane, and -acetylene. Similar radiolysis studies on perfluorocyclobutane , perfluoro-cyclohexane and other perfluoro-compounds show that the dominant process is one of rupture of the carbon-carbon bond with the formation of a variety of perfluoro-compounds as products. 

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