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{{DISPLAYTITLE:Potassium ''tert''-butoxide}} |
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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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{{chembox |
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{{chembox |
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| verifiedrevid = 432345888 |
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| verifiedrevid = 476994881 |
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| Name=Potassium ''tert''-butoxide |
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| ImageFileL1 = Potassium tert-butoxide.png |
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| Name = Potassium ''tert''-butoxide |
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| ImageFileL1 = Potassium tert-butoxide.png |
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| ImageSizeL1 = 115px |
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| ImageNameL1 = Skeletal formula of potassium tert-butoxide |
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| ImageNameL1 = Skeletal formula of potassium tert-butoxide |
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| ImageFileR1 = Potassium-tert-butoxide-3D-balls-ionic.png |
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| ImageFileR1 = Potassium-tert-butoxide-cubane-tetramer-from-xtal-1991-3D-balls.png |
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| ImageNameR1 = Ball-and-stick model of the cubane tetramer that potassium tert-butoxide adopts in |
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| ImageSizeR1 = 125px |
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| ImageNameR1 = Ball-and-stick model of potassium tert-butoxide |
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| ImageFile2 = Potassium-tert-butoxide-3D-balls-ionic.png |
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| ImageSize2 = 180px |
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|IUPACName=potassium 2-methylpropan-2-olate |
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|OtherNames= |
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| OtherNames = KOt-Bu, potassium ''t''-butoxide. |
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| PIN = Potassium ''tert''-butoxide |
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|Section1={{Chembox Identifiers |
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| Section1 = {{Chembox Identifiers |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 63266 |
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| ChemSpiderID = 63266 |
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| InChI = 1/C4H9O.K/c1-4(2,3)5;/h1-3H3;/q-1;+1 |
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| InChI = 1/C4H9O.K/c1-4(2,3)5;/h1-3H3;/q-1;+1 |
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| StdInChIKey = LPNYRYFBWFDTMA-UHFFFAOYSA-N |
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| StdInChIKey = LPNYRYFBWFDTMA-UHFFFAOYSA-N |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo_Ref = {{cascite|correct|CAS}} |
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| CASNo=865-47-4 |
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| CASNo=865-47-4 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| PubChem = 70077 |
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| UNII = VR838VHE0V |
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| SMILES = .C(C)(C)C |
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| PubChem = 70077 |
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| SMILES = .C(C)(C)C |
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|Section2={{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula=C<sub>4</sub>H<sub>9</sub>KO |
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| Formula=C<sub>4</sub>H<sub>9</sub>KO |
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| MolarMass=112.21196 |
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| MolarMass=112.21 g mol<sup>−1</sup> |
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| Appearance= solid |
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| Appearance= solid |
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| MeltingPtC=256 |
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| Density= |
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| BoilingPt_notes=sublimes at 220 °C (1 mmHg) or at 140 °C (0.01 hPa) |
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| MeltingPtC=256 |
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| Solubility = Reacts with water |
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| BoilingPtC= |
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| Solvent1 = diethyl ether |
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| Solubility= |
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| Solubility1 = 4.34 g/100 g (25-26 °C)<ref name=EROS>{{cite encyclopedia | author = Caine D. | encyclopedia = e-EROS Encyclopedia of Reagents for Organic Synthesis | title = Potassium tert-Butoxide | year = 2006| doi = 10.1002/047084289X.rp198.pub2 | chapter = Potassiumtert-Butoxide | isbn = 0471936235}}</ref> |
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| Solvent2 = Hexane |
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|Section3={{Chembox Hazards |
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| Solubility2 = 0.27 g/100 g (25-26 °C)<ref name=EROS/> |
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| ExternalMSDS = |
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| Solvent3 = Toluene |
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| EUClass = Harmful (Xn), Corrosive (C) |
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| Solubility3 = 2.27 g/100 g (25-26 °C)<ref name=EROS/> |
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| FlashPt= |
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| Solvent4 = THF |
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| Autoignition= |
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| Solubility4 = 25.00 g/100 g (25-26 °C)<ref name=EROS/> |
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| Section3 = {{Chembox Hazards |
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| ExternalSDS = |
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| GHSPictograms = {{GHS02}} {{GHS05}} |
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| GHSSignalWord = danger |
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| HPhrases = {{HPhrases|H228|H252|H314}} |
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| EUPhrases = {{EUH-phrases|EUH014}} |
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| PPhrases = {{PPhrases|P405}} |
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| GHS_ref = <ref>{{GESTIS|ZVG=30280|Name=Potassium tert-butoxide|Date=2021-12-22}}</ref> |
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'''Potassium ''tert''-butoxide''' (or '''potassium ''t''-butoxide''') is a ] with the ] <sub>''n''</sub> (abbr. KOtBu). This colourless solid is a strong ] (pKa of conjugate acid around 17), which is useful in ]. The compound is often depicted as a salt, and it often behaves as such, but its ionization depends on the solvent.<ref name=EROS/> |
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==Preparation== |
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Potassium ''t''-butoxide is commercially available as a solution and as a solid, but it is often generated ''in situ'' for laboratory use because samples are so moisture-] and older samples are often of low purity. It is prepared by the reaction of dry ] with ] metal.<ref>{{OrgSynth | author = William S. Johnson and William P. Schneider | title = β-Carbethoxy-γ,γ-diphenylvinylacetic acid | collvol = 4 | collvolpages = 132 | prep = cv4p0132 | year = 1963}}</ref> The solid is obtained by evaporating these solutions followed by heating the solid. The solid can be purified by sublimation. |
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==Structure== |
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It crystallizes as a tetrameric ]. It crystallises from ]/] at −20°C as <sub>∞</sub>, which consists of straight chains linked by ]ing. Sublimation of <sub>∞</sub> affords the tetramer <sub>4</sub>, which adopts a cubane-like structure. Mild ] solvents such as THF and ] do not break up the tetrameric structure, which persists in the solid, in solution and even in the gas phase.<ref>{{ cite journal | first1 = Malcolm H. | last1 = Chisholm | first2 = Simon R. | last2 = Drake | first3 = Ahmad A. | last3 = Naiini | first4 = William E. | last4 = Streib | title = Synthesis and X-ray crystal structures of the one-dimensional ribbon chains <sub>∞</sub> and the cubane species <sub>4</sub> (M = K and Rb) | journal = ] | volume = 10 | issue = 3 | year = 1991 | pages = 337–345 | doi = 10.1016/S0277-5387(00)80154-0}}</ref> |
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==Reactions== |
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===As a base=== |
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Many modifications have been reported that influence the reactivity of this ]. The compound adopts a complex cluster structure (the adjacent picture is a simplified cartoon), and additives that modify the cluster affect the reactivity of the reagent. For example, ], ], ] (HMPA), and ] interact with the potassium center, yielding solvent separated ion pairs such as K(DMSO)<sub>x</sub><sup>+</sup> and ''tert''-BuO<sup>−</sup>. Whereas in benzene, on the other hand, the compound remains as a cluster structure, which is less basic.<ref name=EROS/> Even in polar solvents, it is not as strong as amide bases, e.g., ], but stronger than potassium hydroxide. Its steric bulk inhibits the group from participating in nucleophilic addition, such as in a ] or related ] reactions. {{Citation needed|date=April 2023}} |
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Substrates that are deprotonated by potassium ''t''-butoxide include terminal acetylenes and ]s. It is useful in ] reactions. Illustrating the latter behavior, potassium ''tert''-butoxide reacts with chloroform yielding ], which is useful for dichloro]s.<ref>{{Cite book|url=https://books.google.com/books?id=mTHQB7MkUFsC&dq=tert-butoxide+chloroform&pg=PA551|title=Organic Chemistry|last1=Brown|first1=William|last2=Foote|first2=Christopher|last3=Iverson|first3=Brent|last4=Anslyn|first4=Eric|date=2008-01-10|publisher=Cengage Learning|isbn=978-0495388579|language=en}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=bLV55kunjA4C&dq=tert-butoxide+chloroform&pg=PA119|title=Hazardous Laboratory Chemicals Disposal Guide, Third Edition|author1=Margaret-Ann Armour|author-link=Margaret-Ann Armour|date=2016-04-19|publisher=CRC Press|isbn=9781420032383|language=en}}</ref> Potassium ''tert''-butoxide can abstract a beta-proton from alkylammonium cations, leading to the Hofmann product via an ]. |
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===Other reactions=== |
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Potassium ''tert''-butoxide ] the reaction of ] and heterocyclic compounds to give the silyl derivatives, with release of H<sub>2</sub>.<ref>{{cite journal | author = Anton A. Toutov, Wen-Bo Liu, Kerry N. Betz, Alexey Fedorov, ], ] | journal = Nature | year = 2015 | volume = 518 | issue = 7537 | pages = 80–84 | doi = 10.1038/nature14126 | pmid = 25652999 | title = Silylation of C–H bonds in aromatic heterocycles by an Earth-abundant metal catalyst| bibcode = 2015Natur.518...80T | s2cid = 3117834 | url = https://authors.library.caltech.edu/51898/14/nature14126-s1.pdf}}</ref> |
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==Safety== |
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Potassium ''tert''-butoxide is a very strong base that rapidly attacks living tissue. |
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Potassium ''tert''-butoxide forms explosive mixtures when treated with ].<ref>{{Cite book|url=https://books.google.com/books?id=4IPE8Pjhm8UC&dq=tert-butoxide+dichloromethane&pg=RA3-PT264|title=Hazardous Materials: Emergency Action Data|last1=Foden|first1=Charles R.|last2=Weddell|first2=Jack L.|date=1991-12-29|publisher=CRC Press|isbn=9780873715980|language=en}}</ref> <ref>{{Cite book|url=https://webwiser.nlm.nih.gov/substance?substanceId=48&identifier=Dichloromethane&identifierType=name&menuItemId=7&catId=64|title=Handbook of Reactive Chemical Hazards 4 ed.|last1=Bretherick|first1=L.|date=1990|publisher=Dichloromethane - Reactivities / Incompatibilities in NIH National Library of Medicine|isbn=9781483284668|page=475|language=en}}</ref> |
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==Related compounds== |
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* ] |
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* ] |
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==References== |
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{{Reflist}} |
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