Xenon tetrafluoride synthesis

Xenon tetrafluoride, synthesis 66 Xenon hexafluoride, synthesis 67 Xenon difluoride, synthesis 68... 

Xenon hexafluoride may be prepared in essentially the same way as xenon tetrafluoride (synthesis 66), except for increasing the fluorine-to-xenon ratio and the final pressure at reaction temperature.Variations of temperature, pressure, mol ratio, and time make possible the formation of xenon difluoride, xenon tetrafluoride, or xenon hexafluoride. The conditions described below have been found to give good yields and purity for xenon hexafluoride. 

The starting point for the synthesis of xenon compounds is the preparation of xenon difluoride, XeF2, and xenon tetrafluoride, XeF4, by heating a mixture of the elements to 400°C at 6 atm. At higher pressures, fluorination proceeds as far as xenon hexafluoride, XeFfi. All three fluorides are crystalline solids (Fig. 15.27). In the gas phase, all are molecular compounds. Solid xenon hexafluoride, however, is ionic, with a complex structure consisting of XeF< + cations bridged by F anions. 

Shortly after publication of the observations on the synthesis of xenon tetrafluoride, research was initiated with the noble gases in a number of laboratories. Xenon difluoride, xenon hexafluoride, xenon oxide tetrafluoride, and xenon trioxide were synthesized and reasonably well characterized within a rather short time. A number of other compounds have since been isolated, including xenon tetraoxide, a family of perxenates, and a variety of complex fluorides such as XeF2-2SbF5, XeFe BFs, and CsjXeFs. 

The apparatus and experimental procedures are similar to those used for the tetrafluoride (synthesis 66), except for the use of the heavier-walled vessel H instead of the vessel F. In order to add the required amount of fluorine, it will be necessary either to use a larger vessel G or to repeat the measuring and condensing procedures. The xenon-to-fluorine mol ratios used are about 1 20 [0.689 g. (0.00525 mol) of xenon and 4.18 g. (0.110 mol) of fluorine]. The gas mixture is heated to 300° for 16 hours. The hexafluoride is purified by distillation, the less volatile fraction of lower fluorides being discarded. The purity may be checked by examination of the infrared spectrum, noting the presence of bands at 520 and 612 cm. and the absence of peaks for the difluoride and the tetrafluoride. The spectrum should also be studied in the 900- to 1000-cm. region, where oxyfluorides have fundamentals, for e.xample, XeOF4 at 928 cm. h... 

The purity of the xenon difluoride can be checked by measuring the absorption in the infrared (synthesis 66). Samples prepared as described above, with continuous trapping, contain less than 1 % xenon tetrafluoride, even if the initial fluorine-to-xenon ratio is varied from 0.1 to over 6. 

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