Adams' catalyst: Difference between revisions
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|verifiedrevid = 401789482 |
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|ImageFile = Adams's catalyst.svg |
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|IUPACName = Platinum(IV) oxide |
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|OtherNames = platinum dioxide, platinic oxide |
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|Section1={{Chembox Identifiers |
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|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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|ChemSpiderID = 306130 |
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|InChI = 1/2O.Pt/rO2Pt/c1-3-2 |
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|InChIKey = YKIOKAURTKXMSB-FVLSDXBIAR |
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|StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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|CASNo_Ref = {{cascite|correct|CAS}} |
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|UNII_Ref = {{fdacite|correct|FDA}} |
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|UNII = 9U12312Y2C |
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|Section2={{Chembox Properties |
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|Formula = PtO<sub>2</sub> |
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|MolarMass = 227.08 g/mol |
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|Appearance = black solid |
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|Density = 10.2 g/cm<sup>3</sup> |
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|MeltingPtC = 450 |
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|MagSus = −37.70·10<sup>−6</sup> cm<sup>3</sup>/mol |
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⚫ | '''Adams' catalyst''', also known as '''platinum dioxide''', is usually represented as [[platinum]](IV) [[oxide]] hydrate, PtO<sub>2</sub> |
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|GHSPictograms = {{GHS03}} |
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|GHSSignalWord = '''DANGER''' |
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|HPhrases = {{h-phrases|271}} |
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⚫ | '''Adams' catalyst''', also known as '''platinum dioxide''', is usually represented as [[platinum]](IV) [[oxide]] [[Water of crystallization|hydrate]], PtO<sub>2</sub>•H<sub>2</sub>O. It is a catalyst for [[hydrogenation]] and [[hydrogenolysis]] in [[organic synthesis]].<ref>{{cite book|last1=Nishimura|first1=Shigeo|title=Handbook of Heterogeneous Catalytic Hydrogenation for Organic Synthesis|date=2001|publisher=Wiley-Interscience|location=New York|isbn=9780471396987|pages=30, 32, 64–137, 170–225, 315–386, & 572–663|edition=1st|url=https://books.google.com/books?id=RjZRAAAAMAAJ&q=0471396982}}</ref> This dark brown powder is commercially available. The oxide itself is not an active catalyst, but it becomes active after exposure to hydrogen whereupon it converts to [[platinum black]], which is responsible for reactions. |
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==Preparation== |
==Preparation== |
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Adams' catalyst is prepared from [[chloroplatinic acid]] H<sub>2</sub>PtCl<sub>6</sub> or [[ammonium chloroplatinate]], (NH<sub>4</sub>)<sub>2</sub>PtCl<sub>6</sub>, by fusion with sodium nitrate. The first published preparation was reported by V. Voorhees and [[Roger Adams]].<ref>{{cite journal | author = Voorhees, V. |
Adams' catalyst is prepared from [[chloroplatinic acid]] H<sub>2</sub>PtCl<sub>6</sub> or [[ammonium chloroplatinate]], (NH<sub>4</sub>)<sub>2</sub>PtCl<sub>6</sub>, by fusion with [[sodium nitrate]]. The first published preparation was reported by V. Voorhees and [[Roger Adams]].<ref>{{cite journal | author = Voorhees, V. |author2=Adams, R. | title = The Use of the Oxides of Platinum for the Catalytic Reduction of Organic Compounds | journal = [[J. Am. Chem. Soc.]] | year = 1922 | doi = 10.1021/ja01427a021 | volume = 44 | issue = 6 | pages = 1397|author2-link=Roger Adams |url=https://zenodo.org/record/1428794 }}</ref> The procedure involves first preparing a platinum nitrate which is then heated to expel nitrogen oxides.<ref>{{cite journal|last1=Adams|first1=Roger|last2=Voorhees|first2=V.|last3=Shriner|first3=R. L.|title=Platinum catalyst for reductions|journal=Organic Syntheses|date=1928|volume=8|page=92|doi=10.15227/orgsyn.008.0092}}</ref> |
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:H<sub>2</sub>PtCl<sub>6</sub> + 6 NaNO<sub>3</sub> → Pt(NO<sub>3</sub>)<sub>4</sub> + 6 NaCl <sub>(aq)</sub> + 2 HNO<sub>3</sub> |
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:Pt(NO<sub>3</sub>)<sub>4</sub> → PtO<sub>2</sub> + 4 NO<sub>2</sub> + O<sub>2</sub> |
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The resulting brown cake is washed with water to free it from nitrates. The catalyst can either be used as is or dried and stored in a desiccator for later use. Platinum can be recovered from spent catalyst by conversion to ammonium chloroplatinate using [[aqua regia]] followed by [[ammonia]]. |
The resulting brown cake is washed with water to free it from nitrates. The catalyst can either be used as is or dried and stored in a desiccator for later use. Platinum can be recovered from spent catalyst by conversion to ammonium chloroplatinate using [[aqua regia]] followed by [[ammonia]]. |
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==Uses== |
==Uses== |
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Adams' catalyst is used for many applications. |
Adams' catalyst is used for many applications. It has shown to be valuable for [[hydrogenation]], [[hydrogenolysis]], [[dehydrogenation]], and [[Organic redox reaction|oxidation]] reactions. During the reaction, platinum metal ([[platinum black]]) is formed which has been cited to be the active catalyst.<ref name="Hunt">{{cite journal | last = Hunt | first = LB | title = The Story of Adams' Catalyst: Platinum Oxide in Catalytic Reductions | journal = Platinum Metals Rev. | volume = 6 | issue = 4 | pages = 150–2 | date = October 1962 | url = http://www.platinummetalsreview.com/pdf/pmr-v6-i4-150-152.pdf | access-date = 2007-02-20 | archive-date = 2015-09-24 | archive-url = https://web.archive.org/web/20150924074451/http://www.platinummetalsreview.com/pdf/pmr-v6-i4-150-152.pdf | url-status = dead }}</ref><ref>{{cite journal | doi = 10.1021/jp804870j | last1 = Scheeren | first1 = CW | last2 = Domingos | first2 = Josiel B. | last3 = MacHado | first3 = Giovanna | last4 = Dupont | first4 = Jairton | author4-link = Jairton Dupont | title = Hydrogen Reduction of Adams' Catalyst in Ionic Liquids: Formation and Stabilization of Pt(0) Nanoparticles | journal = J. Phys. Chem. C | volume = 112 | issue = 42 | pages = 16463–9 |date=October 2008}}</ref> Hydrogenation occurs with syn stereochemistry when used on an alkyne resulting in a cis-alkene. Some of the most important transformations include the hydrogenation of ketones to alcohols or [[ether]]s (the latter product forming in the presence of alcohols and acids)<ref>{{cite journal|last1=Verzele|first1=M.|last2=Acke|first2=M.|last3=Anteunis|first3=M.|title=A general synthesis of ethers|journal=Journal of the Chemical Society|date=1963|pages=5598–5600|doi=10.1039/JR9630005598}}</ref> and the [[reduction of nitro compounds]] to amines.<ref>{{cite journal|last1=Adams|first1=Roger|last2=Cohen|first2=F. L.|title=Ethyl p-Aminobenzoate|journal=Organic Syntheses|date=1928|volume=8|page=66|doi=10.15227/orgsyn.008.0066}}</ref> However, reductions of [[alkene]]s can be performed with Adams' catalyst in the presence of nitro groups without reducing the nitro group.<ref>{{cite journal|last1=van Tamelen|first1=Eugene E.|last2=Thiede|first2=Robert J.|title=The Synthetic Application and Mechanism of the Nef Reaction|journal=Journal of the American Chemical Society|date=1952|volume=74|issue=10|pages=2615–2618|doi=10.1021/ja01130a044}}</ref> When reducing nitro compounds to amines, platinum catalysts are preferred over palladium catalysts to minimize hydrogenolysis. The catalyst is also used for the hydrogenolysis of phenyl phosphate esters, a reaction that does not occur with palladium catalysts. The pH of the solvent significantly affects the reaction course, and reactions of the catalyst are often enhanced by conducting the reduction in neat acetic acid, or solutions of acetic acid in other solvents. |
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::PtO<sub>2</sub> + 4 H<sub>2</sub> → Pt + 2 H<sub>2</sub>O |
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==Development== |
==Development== |
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⚫ | <blockquote>"...Several of the problems I assigned my students involved catalytic reduction. For this purpose we were using as a catalyst [[platinum black]] made by the generally accepted best method known at the time. The students had much trouble with the catalyst they obtained in that frequently it proved to be inactive even though prepared by the same detailed procedure which resulted occasionally in an active product. I therefore initiated a research to find conditions for preparing this catalyst with uniform activity."<ref name="Hunt"/></blockquote> |
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⚫ | <blockquote>"... |
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==Safety== |
==Safety== |
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Little precaution is necessary with the oxide but, after exposure to H<sub>2</sub>, the resulting platinum black can be [[pyrophoric]]. Therefore, it should not be allowed to dry and all exposure to oxygen should be minimized. |
Little precaution is necessary with the oxide but, after exposure to H<sub>2</sub>, the resulting platinum black can be [[pyrophoric]]. Therefore, it should not be allowed to dry and all exposure to oxygen should be minimized. |
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==See also== |
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*[[Platinum black]] |
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*[[Rhodium-platinum oxide]] |
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*[[Palladium on carbon]] |
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==References== |
==References== |
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{{Reflist}} |
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<references/> |
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==External links== |
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*[http://www.webelements.com/compounds/platinum/platinum_dioxide.html Platinum compounds: platinum dioxide - WebElements.com] |
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[[Category:Oxides]] |
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[[Category:Catalysts]] |
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{{Platinum compounds}} |
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[[ca:Catalitzador d'Adams]] |
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{{Organic reactions}} |
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[[fr:Catalyseur d'Adams]] |
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[[Category:Platinum(IV) compounds]] |
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[[it:Diossido di platino]] |
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[[Category:Hydrogenation catalysts]] |
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[[ja:アダムス触媒]] |
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[[Category:Transition metal oxides]] |
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[[fi:Platinadioksidi]] |
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[[Category:Transition metal dichalcogenides]] |
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[[zh:二氧化铂]] |