Krypton fluoride
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| Names | |||
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IUPAC name
Krypton(II) fluoride
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| Other names
Krypton fluoride
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| Identifiers | |||
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3D model (JSmol)
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| ChemSpider | |||
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PubChem CID
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| Properties | |||
| F2Kr | |||
| Molar mass | 121.79 g·mol−1 | ||
| Appearance | Colourless crystals (solid) | ||
| Density | 3.24 g cm−3 (solid) | ||
| Reacts | |||
| Structure | |||
| Body-centered tetragonal | |||
| P42/mnm, No. 136 | |||
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a = 0.4585 nm, c = 0.5827 nm
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| Linear | |||
| 0 D | |||
| Related compounds | |||
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Related compounds
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Xenon difluoride | ||
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |||
Krypton difluoride, KrF2 is a chemical compound of krypton and fluorine. It was the first compound of krypton discovered. It is a volatile, colourless solid. The structure of the KrF2 molecule is linear, with Kr−F distances of 188.9 pm. It reacts with strong Lewis acids to form salts of the KrF+ and Kr
2F+
3 cations.
Krypton difluoride can be synthesized using many different methods including electrical discharge, , hot wire, and proton bombardment. The product can be stored at −78 °C without decomposition.
Electric discharge was the first method used to make krypton difluoride. It was also used in the only experiment ever reported to produce krypton tetrafluoride, although the identification of krypton tetrafluoride was later shown to be mistaken. The electrical discharge method involves having 1:1 to 2:1 mixtures of F2 to Kr at a pressure of 40 to 60 torr and then arcing large amounts of energy between it. Rates of almost 0.25 g/h can be achieved. The problem with this method is that it is unreliable with respect to yield.
Using proton bombardment for the production of KrF2 has a maximum production rate of about 1 g/h. This is achieved by bombarding mixtures of Kr and F2 with a proton beam operating at an energy level of 10 MeV and at a temperature of about 133 K. It is a fast method of producing relatively large amounts of KrF2, but requires a source of α-particles, which usually would come from a cyclotron.
The successful photochemical synthesis of krypton difluoride was first reported by Lucia V. Streng in 1963. It was next reported in 1975 by J. Slivnik. The photochemical process for the production of KrF2 involves the use of UV light and can produce under ideal circumstances 1.22 g/h. The ideal wavelengths to use are in the range of 303–313 nm. Harder UV radiation is detrimental to the production of KrF2. Using Pyrex glass or Vycor or quartz will significantly increase yield because they all block harder UV light. In a series of experiments performed by S. A Kinkead et al., it was shown that a quartz insert (UV cut off of 170 nm) produced on average 158 mg/h, Vycor 7913 (UV cut off of 210 nm) produced on average 204 mg/h and Pyrex 7740 (UV cut off of 280 nm) produced on average 507 mg/h. It is clear from these results that higher-energy ultraviolet light reduces the yield significantly. The ideal circumstances for the production KrF2 by a photochemical process appear to occur when krypton is a solid and fluorine is a liquid, which occur at 77 K. The biggest problem with this method is that it requires the handling of liquid F2 and the potential of it being released if it becomes overpressurized.
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