Chlorine trifluoride

It was first reported in 1930 by Ruff and Krug who prepared it by fluorination of chlorine; this also produced chlorine monofluoride (ClF) and the mixture was separated by distillation.{{cite journal|title = Über ein neues Chlorfluorid-CIF₃|author = Otto Ruff, H. Krug|journal = Zeitschrift für anorganische und allgemeine Chemie|year = 1930|volume = 190|issue = 1|pages = 270–276|doi = 10.1002/zaac.19301900127|trans-title=A New Chlorofluoride, ClF₃}}

:{{chem2|3 F2 + Cl2 → 2 ClF3}}

Several hundred tons are produced annually.

The molecular geometry of {{chem2|ClF3}} is approximately T-shaped, with one short bond (1.598 Å) and two long bonds (1.698 Å).{{Cite journal | volume = 21 | issue = 4| pages = 609–614 | journal = The Journal of Chemical Physics | first1 = D. F. | title = The Microwave Spectrum and Structure of Chlorine Trifluoride | year = 1953 | last1 = Smith | doi = 10.1063/1.1698976|bibcode = 1953JChPh..21..609S | hdl = 2027/mdp.39015095092865 | hdl-access = free}} This structure agrees with the prediction of VSEPR theory, which predicts lone pairs of electrons as occupying two equatorial positions of a hypothetic trigonal bipyramid. The elongated Cl-F axial bonds are consistent with hypervalent bonding.

{{chem2|ClF3}} also reacts explosively with water to give hydrogen fluoride and hydrogen chloride, along with oxygen and oxygen difluoride ({{chem2|OF2}}):{{Greenwood&Earnshaw2nd|page=828}}

:{{chem2|ClF3 + H2O → HF + HCl + OF2}}

:{{chem2|ClF3 + 2H2O → 3HF + HCl + O2}}

Upon heating, it decomposes:{{cite book |doi=10.1002/14356007.a11_307 |chapter=Fluorine Compounds, Inorganic |title=Ullmann's Encyclopedia of Industrial Chemistry |date=2000 |last1=Aigueperse |first1=Jean |last2=Mollard |first2=Paul |last3=Devilliers |first3=Didier |last4=Chemla |first4=Marius |last5=Faron |first5=Robert |last6=Romano |first6=René |last7=Cuer |first7=Jean Pierre |isbn=3-527-30673-0 }}

:{{chem2|ClF3 <-> ClF + F2}}

Reactions with many metals and even metal oxides give fluorides:

:{{chem2|6NiO + 4 ClF3 → 6 NiF2 + 3 O2 + 2 Cl2}}

:{{chem2|AgCl + ClF3 → AgF2 + ClF + 1/2 Cl2}}

{{chem2|ClF3}} is used to produce uranium hexafluoride:

:{{chem2|U + 3 ClF3 → UF6 + 3 ClF}}

With phosphorus, it yields phosphorus trichloride ({{chem2|PCl3}}) and phosphorus pentafluoride ({{chem2|PF5}}), while sulfur yields sulfur dichloride ({{chem2|SCl2}}) and sulfur tetrafluoride ({{chem2|SF4}}).

It reacts with caesium fluoride to give a salt containing the anion {{chem2|F(ClF3)3-}}.{{cite journal |last1=Scheibe |first1=Benjamin |last2=Karttunen |first2=Antti J. |last3=Müller |first3=Ulrich |last4=Kraus |first4=Florian |title=Cs[Cl 3 F 10 ]: A Propeller-Shaped [Cl 3 F 10 ] − Anion in a Peculiar A [5] B [5] Structure Type |journal=Angewandte Chemie International Edition |date=5 October 2020 |volume=59 |issue=41 |pages=18116–18119 |doi=10.1002/anie.202007019|pmid=32608053 |pmc=7589245 |doi-access=free }}

In the semiconductor industry, chlorine trifluoride is used to clean chemical vapour deposition chambers. It can be used to remove semiconductor material from the chamber walls without the need to dismantle the chamber. Unlike most of the alternative chemicals used in this role, it does not need to be activated by the use of plasma since the heat of the chamber is sufficient to make it decompose and react with the semiconductor material.

ClF₃ is used for the fluorination of a variety of compounds.

Chlorine trifluoride has been investigated as a high-performance storable oxidizer in rocket propellant systems. Handling concerns, however, severely limit its use. The following passage by rocket scientist John D. Clark is widely quoted in descriptions of the substance's extremely hazardous nature:

It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water—with which it reacts explosively. It can be kept in some of the ordinary structural metals—steel, copper, aluminum, etc.—because of the formation of a thin film of insoluble metal fluoride that protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.{{Cite book | last = Clark | first = John D. | author-link = John Drury Clark | title = Ignition! An Informal History of Liquid Rocket Propellants | publisher = Rutgers University Press | year = 1972 | page = 214 | isbn = 978-0-8135-0725-5 }}

Chlorine pentafluoride (ClF₅) has also been investigated as a potential rocket oxidizer. It offered improved specific impulse over chlorine trifluoride, but with all of the same difficulties in handling. Neither compound has been used in any operational rocket propulsion system.

Under the code name N-Stoff ("substance N"), chlorine trifluoride was investigated for military applications by the Kaiser Wilhelm Institute in Nazi Germany not long before the start of World War II. Tests were made against mock-ups of the Maginot Line fortifications, and it was found to be an extremely effective incendiary weapon and poison gas. From 1938, construction commenced on a partly bunkered, partly subterranean {{Convert|14,000|m2|sqft|abbr=on}} munitions factory, the Falkenhagen industrial complex, which was intended to produce 90 tonnes of N-Stoff per month, in addition to sarin (a deadly nerve agent). However, by the time it was captured by the advancing Red Army in 1945, the factory had produced only about 30 to 50 tonnes, at a cost of over 100 German Reichsmarks per kilogram.{{ref|a|a}} N-Stoff was never used in war.{{r|Muller-2005-11-24}}{{cite web|url=http://www.bunkertours.co.uk/germany_2004.htm|title=Germany 2004|website=www.bunkertours.co.uk|access-date=2006-06-13|archive-date=2006-06-13|archive-url=https://web.archive.org/web/20060613045929/http://bunkertours.co.uk/germany_2004.htm|url-status=live}}

{{chem2|ClF3}} is a very strong oxidizer. It is extremely reactive with most inorganic and organic materials and will combust many otherwise non-flammable materials without any ignition source. These reactions are often violent and in some cases explosive. Steel, copper, and nickel are not consumed because a passivation layer of metal fluoride will form which prevents further corrosion, but molybdenum, tungsten, and titanium are unsuitable as their fluorides are volatile. {{chem2|ClF3}} will quickly corrode even noble metals like iridium, platinum, or gold, oxidizing them to chlorides and fluorides.

This oxidizing power, surpassing that of oxygen, causes {{chem2|ClF3}} to react vigorously with many other materials often thought of as incombustible and refractory. It ignites sand, asbestos, glass, and even ashes of substances that have already burned in oxygen. In one particular industrial accident, a spill of 900 kg of {{chem2|ClF3}} burned through 30 cm of concrete and 90 cm of gravel beneath.[https://web.archive.org/web/20060318221608/http://www.airproducts.com/nr/rdonlyres/8479ed55-2170-4651-a3d4-223b2957a9f3/0/safetygram39.pdf Safetygram]. Air Products There is exactly one known fire control/suppression method capable of dealing with {{nowrap|{{chem2|ClF3}}{{px2}}{{mdash}}{{px2}}}}flooding the fire with nitrogen or noble gases such as argon. Barring that, the area must simply be kept cool until the reaction ceases.{{cite web |url=http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0266121 |title=Chlorine Trifluoride Handling Manual |date=September 1961 |publisher=Rocketdyne |location=Canoga Park, CA |page=24 |access-date=2012-09-19 |archive-date=2013-04-08 |archive-url=https://web.archive.org/web/20130408133311/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0266121 }} The compound reacts with water-based suppressors and CO₂, rendering them counterproductive.{{cite book|title = A comprehensive guide to the hazardous properties of chemical substances|author = Patnaik, Pradyot|edition = 3rd|publisher = Wiley-Interscience|year = 2007|isbn = 978-0-471-71458-3|page = 478}}

Exposure to larger amounts of {{chem2|ClF3}}, as a liquid or as a gas, ignites living tissue, resulting in severe chemical and thermal burns. {{chem2|ClF3}} reacts violently with water and exposure to the reaction also results in burns. The products of hydrolysis are mainly hydrofluoric acid and hydrochloric acid, which are usually released as steam or vapor due to the highly exothermic nature of the reaction, and these substances present hazards of their own.

• Chlorine fluoride
• Dioxygen difluoride
• List of stoffs

{{Note|a|a}} Using data from Economic History Services{{Citation |last=Officer |first=Lawrence H. |date=2002 |title=Exchange Rate Between the United States Dollar and Forty Other Countries, 1913–1999 |url=http://eh.net/hmit/exchangerates/ |archive-url=https://web.archive.org/web/20060615032843/http://eh.net/hmit/exchangerates/ |archive-date=15 June 2006 |publisher=EH.net (Economic History Services) |access-date=7 July 2023}} and The Inflation Calculator{{Cite web |title=The Inflation Calculator |url=http://www.westegg.com/inflation/ |publisher=S. Morgan Friedman's 'Webpage': Ceci N'est Pas Une Homepage |access-date=7 July 2023}} it can be calculated that the sum of 100 Reichsmarks in 1941 is approximately equivalent to US$4,652.50 in 2021. Reichsmark exchange rate values from 1942 to 1944 are fragmentary.

{{reflist | 30em | refs =

{{cite journal|author-last = Müller|author-first = Benno|date = 24 November 2005|title = A poisonous present|journal = Nature|series = Review of: Kampfstoff-Forschung im Nationalsozialismus: Zur Kooperation von Kaiser-Wilhelm-Instituten, Militär und Industrie [Weapons Research in National Socialism] by Florian Schmaltz (Wallstein, 2005, 676 pages)|volume = 438|issue = 7067|page = 427|doi = 10.1038/438427a|bibcode = 2005Natur.438..427M|doi-access= free}}

}}

{{refbegin}}

• {{cite book|last = Groehler|first = Olaf|title = Der lautlose Tod. Einsatz und Entwicklung deutscher Giftgase von 1914 bis 1945|publisher = Rowohlt|year = 1989|location = Reinbek bei Hamburg|isbn= 978-3-499-18738-4}}
• {{cite book|last = Ebbinghaus|first = Angelika|title = Krieg und Wirtschaft: Studien zur deutschen Wirtschaftsgeschichte 1939–1945|publisher = Metropol|pages = 171–194|year = 1999|location = Berlin|isbn= 978-3-932482-11-3}}
• {{cite journal|title = The Halogen Fluorides|journal = Chemical Reviews|year = 1947|volume = 41|issue = 3|pages = 421–439|doi = 10.1021/cr60130a001|last1 = Booth|first1 = Harold Simmons|last2 = Pinkston|first2 = John Turner Jr.|pmid = 18895518}}
• {{cite journal|title = Physicochemical Properties of Chlorine Trifluoride|author1=Yu D Shishkov|author2=A A Opalovskii|journal = Russian Chemical Reviews|year = 1960|volume = 29|issue = 6|pages = 357–364|doi = 10.1070/RC1960v029n06ABEH001237|bibcode = 1960RuCRv..29..357S|s2cid=250863587}}
• {{cite journal|title = The Structures of the Interhalogen Compounds. I. Chlorine Trifluoride at −120 °C|author1=Robinson D. Burbank|author2=Frank N. Bensey|journal = The Journal of Chemical Physics|year = 1953|volume = 21|issue = 4|pages = 602–608|doi = 10.1063/1.1698975|bibcode = 1953JChPh..21..602B}}
• {{cite journal|title = The determination of the liquid density of chlorine trifluoride|author1=A. A. Banks |author2=A. J. Rudge|journal = Journal of the Chemical Society|year = 1950|pages = 191–193|doi = 10.1039/JR9500000191}}
• {{cite journal|title = Pilot plant study of fluorine and its derivatives|author1=Lowdermilk, F. R.|author2=Danehower, R. G.|author3=Miller, H. C.|journal = Journal of Chemical Education|year = 1951|volume = 28|issue =5|page = 246|doi =10.1021/ed028p246|bibcode = 1951JChEd..28..246L}}

{{refend}}

• [http://www.npi.gov.au/substances/fluoride-compounds/index.html National Pollutant Inventory – Fluoride and compounds fact sheet]
• [http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]
• [https://www.cdc.gov/niosh/npg/npgd0117.html CDC – NIOSH Pocket Guide to Chemical Hazards – Chlorine Trifluoride]
• [http://www.webelements.com/ WebElements]
• [https://www.science.org/content/blog-post/sand-won-t-save-you-time Sand Won't Save You This Time], blog post by Derek Lowe on the hazards of handling {{chem2|ClF3}}
• [https://onlinelibrary.wiley.com/action/downloadSupplement?10.1002/anie.201915245&file=anie202007019-s1-Cl3F10_Supporting_Information_-_accepted.pdf]{{Dead link|date=July 2023}}

{{Chemical agents}}

{{Chlorine compounds}}

{{Fluorine compounds}}

Category:Chlorine(III) compounds

Category:Fluorides

Category:Fluorinating agents

Category:Incendiary weapons

Category:Inorganic chlorine compounds

Category:Interhalogen compounds

Category:Oxidizing agents

Category:Rocket oxidizers

Category:Substances discovered in the 1930s