| Revision as of 13:35, 15 February 2012 editBeetstra (talk | contribs)Edit filter managers, Administrators172,031 edits Saving copy of the {{chembox}} taken from revid 472280549 of page Krypton_difluoride for the Chem/Drugbox validation project (updated: 'CASNo'). |
Latest revision as of 22:58, 26 November 2024 edit 19Fluor (talk | contribs)7 editsm Reference to publication in J. Fluorine Chem. was added.Tag: Visual edit |
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{{ambox | text = This page contains a copy of the infobox ({{tl|chembox}}) taken from revid of page ] with values updated to verified values.}} |
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| verifiedrevid = 437131613 |
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| verifiedrevid = 477002066 |
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| ImageFileL1 = Krypton-difluoride-2D-dimensions.png |
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| ImageFileL1 = Krypton-difluoride-2D-dimensions.png |
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| ImageFileL1_Ref = {{chemboximage|correct|??}} |
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| ImageFileL1_Ref = {{chemboximage|correct|??}} |
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| ImageSizeR1 = 121 |
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| ImageSizeR1 = 121 |
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| ImageNameR1 = Spacefill model of krypton difluoride |
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| ImageNameR1 = Spacefill model of krypton difluoride |
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| IUPACName = Krypton(II) fluoride |
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| IUPACName = {{PAGENAME}} |
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| OtherNames = Krypton fluoride |
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| OtherNames = Krypton fluoride<br/>Krypton(II) fluoride |
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| Section1 = {{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo = <!-- blanked - oldvalue: 13773-81-4 --> |
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| CASNo = 13773-81-4 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| UNII = A91DJL4OJC |
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| PubChem = 83721 |
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| PubChem = 83721 |
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| PubChem_Ref = {{Pubchemcite|correct|pubchem}} |
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| ChemSpiderID = 75543 |
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| ChemSpiderID = 75543 |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| SMILES = FF |
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| SMILES = FF |
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| StdInChI = 1S/F2Kr/c1-3-2 |
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| StdInChI = 1S/KrF2/c1-3-2 |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| InChI = 1/F2Kr/c1-3-2 |
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| InChI = 1/F2Kr/c1-3-2 |
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| InChIKey = QGOSZQZQVQAYFS-UHFFFAOYAJ |
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| InChIKey = QGOSZQZQVQAYFS-UHFFFAOYAJ |
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| Section2 = {{Chembox Properties |
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|Section2={{Chembox Properties |
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| F = 2 |
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| Kr=1 | F=2 |
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| Kr = 1 |
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| ExactMass = 121.908313037 g mol<sup>−1</sup> |
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| Appearance = Colourless crystals (solid) |
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| Appearance = Colourless crystals (solid) |
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| Density = 3.24 g cm<sup>−3</sup> (solid) |
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| Density = 3.24 g cm<sup>−3</sup> (solid) |
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| Solubility = Reacts |
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| Solubility = Reacts |
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| Section3 = {{Chembox Structure |
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|Section3={{Chembox Structure |
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| MolShape = Linear |
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| MolShape = Linear |
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| CrystalStruct = Body-centered tetragonal<ref>{{cite journal|journal=Science|year=1972|volume=178 |issue=4067|pages=1285–1286|doi=10.1126/science.178.4067.1285|title= Crystal Structure of Krypton Difluoride at −80°C|author=R. D. Burbank, W. E. Falconer and W. A. Sunder|pmid=17792123}}</ref> |
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| CrystalStruct = Body-centered tetragonal<ref>{{cite journal|journal=Science|year=1972|volume=178 |issue=4067|pages=1285–1286|doi=10.1126/science.178.4067.1285|title= Crystal Structure of Krypton Difluoride at −80 °C|author=R. D. Burbank, W. E. Falconer and W. A. Sunder|pmid=17792123|s2cid=96692996}}</ref> |
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| Dipole = 0 D |
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| Dipole = 0 D |
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| SpaceGroup = P4<sub>2</sub>/mnm, No. 136 |
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| SpaceGroup = P4<sub>2</sub>/mnm, No. 136 |
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| LattConst_c = 0.5827 nm |
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| LattConst_c = 0.5827 nm |
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| Section8 = {{Chembox Related |
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| OtherCpds = ] |
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| OtherCompounds = ] |
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'''Krypton difluoride''', KrF<sub>2</sub> is a chemical compound of ] and ]. It was the first ] of krypton discovered.<ref>{{cite journal|doi=10.1126/science.139.3559.1047|title=Krypton Tetrafluoride: Preparation and Some Properties|year=1963|last1=Grosse|first1=A. V.|last2=Kirshenbaum|first2=A. D.|last3=Streng|first3=A. G.|last4=Streng|first4=L. V.|journal=Science|volume=139|issue=3559|pages=1047–8|pmid=17812982|bibcode=1963Sci...139.1047G}}</ref> It is a ], colourless solid at room temperature. The structure of the KrF<sub>2</sub> molecule is linear, with Kr−F distances of 188.9 pm. It reacts with strong ]s to form salts of the KrF<sup>+</sup> and Kr{{su|b=2}}{{chem|F|3|+}} ]s.<ref name="Lehmann" /> |
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The atomization energy of KrF<sub>2</sub> (KrF<sub>2(g)</sub> → Kr<sub>(g)</sub> + 2 F<sub>(g)</sub>) is 21.9 kcal/mol, giving an average Kr–F bond energy of only 11 kcal/mol,<ref>The values of ''D''<sub>e</sub>(F–KrF) and ''D''<sub>e</sub>(F–Kr•) are estimated to be comparable, at ~10-12 kcal/mol, while Δ''H''(KrF<sup>+</sup> → Kr<sup>+</sup> + F•) is estimated to be ~42 kcal/mol.</ref> the weakest of any isolable fluoride. In comparison, the dissociation of difluorine to atomic fluorine requires cleaving a F–F bond with a bond dissociation energy of 36 kcal/mol. Consequently, KrF<sub>2</sub> is a good source of the extremely reactive and oxidizing atomic fluorine. It is thermally unstable, with a decomposition rate of 10% per hour at room temperature.<ref name=":0">{{Cite book|title=The Chemistry of the Monatomic Gases: Pergamon Texts in Inorganic Chemistry|last1=Cockett|first1=A. H.|last2=Smith|first2=K. C.|last3=Bartlett|first3=Neil|publisher=Pergamon Press|year=1973|isbn=978-0-08-018782-2}}</ref> The formation of krypton difluoride is endothermic, with a heat of formation (gas) of 14.4 ± 0.8 kcal/mol measured at 93 °C.<ref name=":0" /> |
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==Synthesis== |
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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.<ref name="Holl">{{Holleman&Wiberg}}</ref> |
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===Electrical discharge=== |
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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 F<sub>2</sub> 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.<ref name="Lehmann">{{cite journal|last1=Lehmann|first1=J|title=The chemistry of krypton|journal=Coordination Chemistry Reviews|date=1 November 2002|volume=233–234|pages=1–39|doi=10.1016/S0010-8545(02)00202-3}}</ref><ref name="Kinkead">{{cite book | author1 = Kinkead, S. A. | author2 = Fitzpatrick, J. R. | author3 = Foropoulos, J. Jr. | author4 = Kissane, R. J. | author5 = Purson, D. | chapter = 3. Photochemical and thermal Dissociation Synthesis of Krypton Difluoride | title = Inorganic Fluorine Chemistry: Toward the 21st Century | publisher = American Chemical Society | location = San Francisco, California | year = 1994 | pages = 40–54 |isbn=978-0-8412-2869-6|doi=10.1021/bk-1994-0555.ch003}}</ref> |
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===Proton bombardment=== |
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Using proton bombardment for the production of KrF<sub>2</sub> has a maximum production rate of about 1 g/h. This is achieved by bombarding mixtures of Kr and F<sub>2</sub> 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 KrF<sub>2</sub>, but requires a source of high-energy protons, which usually would come from a ].<ref name="Lehmann" /><ref>{{Cite journal | doi = 10.1021/ic50038a048 | title = Synthesis of Noble Gas Compounds by Proton Bombardment | year = 1966 | last1 = MacKenzie | first1 = D. R. | last2 = Fajer | first2 = J. | journal = Inorganic Chemistry | volume = 5 | issue = 4| pages = 699–700}}</ref> |
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===Photochemical=== |
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The successful photochemical synthesis of krypton difluoride was first reported by ] in 1963. It was next reported in 1975 by J. Slivnik.<ref>{{Cite journal |last=Slivnik |first=Joẑe |last2=Šmalc |first2=Andrej |last3=Lutar |first3=Karel |last4=Ẑemva |first4=Boris |last5=Frlec |first5=Boris |date=1974-12-10 |title=A new method for the preparation of krypton difluoride |url=https://linkinghub.elsevier.com/retrieve/pii/S0022113900824884 |journal=Journal of Fluorine Chemistry |language=en |volume=5 |issue=3 |pages=273–274 |doi=10.1016/S0022-1139(00)82488-4}}</ref><ref>{{cite book|last1=Xu|first1=Ruren|last2=Pang|first2=Wenqin|last3=Huo|first3=Qisheng|title=Modern Inorganic Synthetic Chemistry|date=2010|publisher=Elsevier Science|location=Burlington|isbn=9780444536006|page=54|url=https://books.google.com/books?id=mJBW5pLF5R8C&pg=PA54|access-date=8 April 2017}}</ref><ref>{{cite news|last=Jaffe |first=Mark |title=Lucia V. Streng, 85; Innovative Chemist At Temple University |newspaper=] |date=April 30, 1995 |url=http://articles.philly.com/1995-04-30/news/25687426_1_krypton-painting-china-chemist |access-date=24 August 2016 |archive-url=https://archive.today/20160316100623/http://articles.philly.com/1995-04-30/news/25687426_1_krypton-painting-china-chemist |archive-date=16 March 2016 |url-status=dead }}</ref><ref name="Lehmann" /> The photochemical process for the production of KrF<sub>2</sub> 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 KrF<sub>2</sub>. 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 KrF<sub>2</sub> 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 F<sub>2</sub> and the potential of it being released if it becomes overpressurized.<ref name="Lehmann" /><ref name="Kinkead" /> |
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===Hot wire=== |
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The hot wire method for the production of KrF<sub>2</sub> uses krypton in a solid state with a hot wire running a few centimeters away from it as fluorine gas is then run past the wire. The wire has a large current, causing it to reach temperatures around 680 °C. This causes the fluorine gas to split into its radicals, which then can react with the solid krypton. Under ideal conditions, it has been known to reach a maximum yield of 6 g/h. In order to achieve optimal yields the gap between the wire and the solid krypton should be 1 cm, giving rise to a temperature gradient of about 900 °C/cm. A major downside to this method is the amount of electricity that has to be passed through the wire. It is dangerous if not properly set up.<ref name="Lehmann" /><ref name="Kinkead" /> |
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==Structure== |
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] |
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Krypton difluoride can exist in one of two possible crystallographic morphologies: α-phase and β-phase. β-KrF<sub>2</sub> generally exists at above −80 °C, while α-KrF<sub>2</sub> is more stable at lower temperatures.<ref name="Lehmann" /> The unit cell of α-KrF<sub>2</sub> is body-centred tetragonal. |
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==Reactions== |
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Krypton difluoride is primarily a powerful oxidising and fluorinating agent, more powerful even than elemental fluorine because Kr–F has less ]. It has a redox potential of +3.5 V for the KrF<sub>2</sub>/Kr couple,{{cn|date=December 2023}} making it the most powerful known oxidising agent. However, the hypothetical ] could be even stronger<ref name="henderson">{{cite book| title = Main group chemistry| url = https://archive.org/details/maingroupchemist00hend_891| url-access = limited| author = W. Henderson| location = Great Britain| publisher = Royal Society of Chemistry| year = 2000| isbn = 0-85404-617-8| page = }}</ref> and ] comes close. |
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For example, krypton difluoride can oxidise ] to its highest-known oxidation state, +5: |
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: {{chem2|7 KrF2 + 2 Au → 2 KrF+AuF6− + 5 Kr}} |
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KrF{{su|p=+}}AuF{{su|b=6|p=−}} decomposes at 60 °C into ] and krypton and fluorine gases:<ref>{{cite book| title = Elements of the ''p'' block| author = Charlie Harding| author2 = David Arthur Johnson| author3 = Rob Janes| location = Great Britain|publisher = Royal Society of Chemistry| year = 2002| isbn = 0-85404-690-9| page = 94}}</ref> |
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: {{chem2| → AuF5 + Kr + F2}} |
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{{chem|KrF|2}} can also directly oxidise ] to ]:<ref name="henderson" /> |
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: {{chem2|3 KrF2 + Xe → XeF6 + 3 Kr}} |
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{{chem|KrF|2}} is used to synthesize the highly reactive BrF{{su|b=6|p=+}} cation.<ref name="Holl" /> {{chem|KrF|2}} reacts with {{chem|SbF|5}} to form the salt KrF{{su|p=+}}SbF{{su|b=6|p=−}}; the KrF{{su|p=+}} cation is capable of oxidising both ] and ] to BrF{{su|b=6|p=+}} and ClF{{su|b=6|p=+}}, respectively.<ref>{{cite book| title = Advances in Inorganic Chemistry| url = https://archive.org/details/isbn_0120236451| url-access = limited| author = John H. Holloway| author2 = Eric G. Hope| editor = A. G. Sykes| publisher = Academic Press| year = 1998| isbn = 0-12-023646-X| pages =–61}}</ref> |
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{{chem|Kr|F|2}} can also react with elemental silver to produce ].<ref>{{cite book | title = Chemistry of the Elements | author1 = A. Earnshaw | author2 = Norman Greenwood | edition = 2nd | publisher = Elsevier | year = 1997 | isbn = 9780080501093 | page = 903}}</ref><ref>{{cite journal|doi=10.1021/ic00190a049 | volume=23 | issue=22 | title=Synthesis and properties of silver trifluoride AgF3 | journal=Inorganic Chemistry | pages=3667–3668 | last1 = Bougon | first1 = Roland| year=1984}}</ref> |
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Irradiation of a crystal of KrF<sub>2</sub> at 77 K with γ-rays leads to the formation of the krypton monofluoride radical, KrF•, a violet-colored species that was identified by its ] spectrum. The radical, trapped in the crystal lattice, is stable indefinitely at 77 K but decomposes at 120 K.<ref>{{Cite journal|last1=Falconer|first1=W. E.|last2=Morton|first2=J. R.|last3=Streng|first3=A. G.|date=1964-08-01|title=Electron Spin Resonance Spectrum of KrF|journal=The Journal of Chemical Physics|volume=41|issue=3|pages=902–903|doi=10.1063/1.1725990|issn=0021-9606|bibcode=1964JChPh..41..902F}}</ref> |
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==See also== |
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*] |
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== References == |
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{{reflist | 30em}} |
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==General reading== |
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* {{Greenwood&Earnshaw}} |
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==External links== |
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{{Krypton compounds}} |
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{{fluorine compounds}} |
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] |
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