Просмотр кода страницы Английская Википедия:Ceric ammonium nitrate

{{Английская Википедия/Панель перехода}}
{{chembox
|Name = Ammonium cerium(IV) nitrate
|ImageFile = Ceric ammonium nitrate.jpg
|ImageName = Ammonium cerium(IV) nitrate
|IUPACName = Diammonium cerium(IV) nitrate
|OtherNames = Ceric ammonium nitrate<br>CAN<br>Diammonium hexanitratocerate(IV)
|Section1={{Chembox Identifiers
|CASNo = 16774-21-3
|CASNo_Ref = {{cascite|correct|CAS}}
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = U99S55ED6B
|EINECS = 240-827-6
|PubChem = 180504
|ChemSpiderID = 157072
|SMILES = [Ce+4].O=[N+]([O-])[O-].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[NH4+].[NH4+]
|InChI = 1/Ce.6NO3.2H3N/c;6*2-1(3)4;;/h;;;;;;;2*1H3/q+4;6*-1;;/p+2
|InChIKey = XMPZTFVPEKAKFH-SKRXCDHZAV
|StdInChI = 1S/Ce.6NO3.2H3N/c;6*2-1(3)4;;/h;;;;;;;2*1H3/q+4;6*-1;;/p+2
|StdInChIKey = XMPZTFVPEKAKFH-UHFFFAOYSA-P
}}
|Section2={{Chembox Properties
|Formula = {{chem2|[NH4]2[Ce(NO3)6]}}
|H=8|N=8|Ce=1|O=18
|Appearance = orange-red crystals
|Solubility = 141 g/100 mL (25&nbsp;°C)<br />227 g/100 mL (80&nbsp;°C)
|MeltingPtC = 107 to 108
}}
|Section3={{Chembox Structure
|Coordination = [[Icosahedral]]
|CrystalStruct = [[Monoclinic]]
}}
|Section4={{Chembox Hazards
|GHSPictograms={{GHS03}}{{GHS07}}<ref>{{Sigma-Aldrich|aldrich|id=229547|name=Ammonium cerium(IV) nitrate|accessdate=2015-05-13}}</ref>
|GHSSignalWord=Danger
|HPhrases={{H-phrases|272|302|315|319|335}}
|PPhrases={{P-phrases|220|261|305+351+338}}
}}
|Section5={{Chembox Related
|OtherCompounds = [[Ammonium nitrate]]<br /> [[Cerium(IV) oxide]]
}}
}}

'''Ceric ammonium nitrate''' (CAN) is the [[inorganic compound]] with the formula {{chem2|[[Ammonium|(NH4)]]2[Ce(NO3)6]}}. This orange-red, water-soluble [[cerium]] [[salt (chemistry)|salt]] is a specialised [[Redox|oxidizing agent]] in [[organic synthesis]] and a standard oxidant in [[quantitative analysis (chemistry)|quantitative analysis]].

==Preparation, properties, and structure==
The [[anion]] {{chem2|[Ce(NO3)6](2-)}} is generated by dissolving [[cerium(III) oxide|{{chem2|Ce2O3}}]] in hot and concentrated [[nitric acid]] ({{chem2|HNO3}}).<ref>{{Cite journal |last=Smith |first=G.Frederick |date=June 1963 |title=An improved preparation of ammonium hexanitratocerate(IV) and routine analytical testing procedure to prove primary reference standard purity |url=https://linkinghub.elsevier.com/retrieve/pii/0039914063800934 |journal=Talanta |language=en |volume=10 |issue=6 |pages=709–710 |doi=10.1016/0039-9140(63)80093-4}}</ref>

The salt consists of the hexanitratocerate(IV) anion {{chem2|[Ce(NO3)6](2-)}} and a pair of [[ammonium]] cations {{chem2|NH4+}}. The ammonium ions are not involved in the oxidising reactions of this salt. In the anion each nitrate group [[chelate]]s the cerium atom in a [[bidentate]] manner as shown below:

{{multiple image
 | align = none
 | direction = horizontal
 | total_width = 400
 | image1 = Hexanitratocerat.svg
 | caption1 = Hexanitratocerate anion
 | image2 = Hexanitratocerate(IV)-ion-from-CAN-xtal-3D-bs-17.png
 | caption2 = [[Ball-and-stick model]]<ref>{{Cite journal | url = https://www.ccdc.cam.ac.uk/structures/Search?Ccdcid=1598999&DatabaseToSearch=Published | title = CSD Entry 1598999, ICSD Entry 22219, H<sub>8</sub>CeN<sub>8</sub>O<sub>18</sub> | website = [[Cambridge Structural Database]]: Access Structures | publisher = [[Cambridge Crystallographic Data Centre]] | access-date = 2021-11-05}}</ref><ref name="Beineke&Delgaudio"/>
}}

The anion {{chem2|[Ce(NO3)6](2-)}} has T<sub>h</sub> (idealized O<sub>h</sub>) [[molecular symmetry]]. The {{chem2|CeO12}} core defines an [[icosahedron]].<ref name="Beineke&Delgaudio">{{cite journal | author = Thomas A. Beineke | author2 = J. Delgaudio | year = 1968 | title = Crystal structure of ceric ammonium nitrate | journal = Inorg. Chem. | volume = 7 | issue = 4 | pages = 715–721 | doi = 10.1021/ic50062a020 }}</ref>

{{chem2|Ce(4+)}} is a strong one-electron [[oxidizing agent]]. In terms of its redox potential ({{nowrap|''E''° ≈ 1.61 V}} vs. [[Normal hydrogen electrode|N.H.E.]]) it is an even stronger oxidizing agent than [[Chlorine|{{chem2|Cl2}}]] ({{nowrap|''E''° ≈ 1.36 V}}). Few shelf-stable reagents are stronger oxidants. In the redox process Ce(IV) is converted to Ce(III), a one-electron change, signaled by the fading of the solution color from orange to a pale yellow (providing that the substrate and product are not strongly colored).

==Applications in organic chemistry==
In organic synthesis, CAN is useful as an oxidant for many functional groups ([[alcohols]], [[phenol]]s, and [[ether]]s) as well as C–H bonds, especially those that are benzylic. [[Alkene]]s undergo dinitroxylation, although the outcome is solvent-dependent. [[Quinone]]s are produced from [[catechols]] and [[hydroquinone]]s and even [[nitroalkane]]s are oxidized.<ref>{{cite journal |doi=10.1021/cr068408n|title=Cerium(IV) Ammonium NitrateA Versatile Single-Electron Oxidant |year=2007 |last1=Nair |first1=Vijay |last2=Deepthi |first2=Ani |journal=Chemical Reviews |volume=107 |issue=5 |pages=1862–1891 |pmid=17432919 }}</ref><ref>{{cite journal |doi=10.1021/cr100004p|title=Cerium(IV) Ammonium Nitrate as a Catalyst in Organic Synthesis |year=2010 |last1=Sridharan |first1=Vellaisamy |last2=Menéndez |first2=J. Carlos |journal=Chemical Reviews |volume=110 |issue=6 |pages=3805–3849 |pmid=20359233 }}</ref>

CAN provides an alternative to the [[Nef reaction]]; for example, for [[ketomacrolide]] synthesis where complicating side reactions usually encountered using other reagents. Oxidative halogenation can be promoted by CAN as an ''in situ'' oxidant for benzylic bromination, and the iodination of ketones and [[uracil]] derivatives.

===For the synthesis of heterocycles===
Catalytic amounts of aqueous CAN allow the efficient synthesis of [[quinoxaline]] derivatives. Quinoxalines are known for their applications as dyes, [[organic semiconductor]]s, and DNA cleaving agents. These derivatives are also components in antibiotics such as [[echinomycin]] and [[actinomycin]]. The CAN-catalyzed three-component reaction between [[aniline]]s and [[alkyl vinyl ether]]s provides an efficient entry into 2-methyl-1,2,3,4-tetrahydroquinolines and the corresponding [[quinoline]]s obtained by their [[aromatization]].

===As a deprotection reagent===
CAN is traditionally used to release organic ligands from [[metal carbonyl]]s. In the process, the metal is oxidised, CO is evolved, and the organic ligand is released for further manipulation.<ref>L. Brener, J. S. McKennis, and R. Pettit "Cyclobutadiene in Synthesis: ''endo''-Tricyclo[4.4.0.0<sup>2,5</sup>]deca-3,8-diene-7,10-dione" Org. Synth. 1976, 55, 43.{{doi|10.15227/orgsyn.055.0043}}</ref> For example, with the [[Wulff–Dötz reaction]] an alkyne, carbon monoxide, and a chromium [[carbene]] are combined to form a chromium [[half-sandwich complex]]<ref>{{cite journal|last1 = Waters|first1 = M.|first2 = W. D.|last2 = Wulff|title = The Synthesis of Phenols and Quinones via Fischer Carbene Complexes|journal = [[Organic Reactions]]|date = 2008|volume = 70|issue = 2|pages = 121–623|doi = 10.1002/0471264180.or070.02}}</ref><ref>{{cite journal|last1 = Dötz|first1 = K. H.|title = Carbon–Carbon Bond Formation via Carbonyl-Carbene Complexes|journal = [[Pure and Applied Chemistry]]|date = 1983|volume = 55|issue = 11| pages=1689–1706 |doi=10.1351/pac198355111689| s2cid=95165461 |doi-access = free}}</ref> and the phenol ligand can be isolated by mild CAN oxidation.
:[[Image:Wulff–Dötz reaction to a chromium half-sandwich complex.png|700px]]

CAN is used to cleave ''para''-methoxybenzyl and 3,4-dimethoxybenzyl ethers, which are [[protecting group]]s for alcohols.<ref name="boons">Boons, Geert-Jan.; Hale, Karl J. (2000). ''Organic Synthesis with Carbohydrates'' (1st ed.) Sheffield, England: Sheffield Academic Press. pp.33</ref><ref name="kocienski">Kocienski, Phillip J. (1994). ''Protecting Groups'' Stuttgart, New York Georg Thieme Verlag. pp 8–9, 52–54</ref> Two equivalents of CAN are required for each equivalent of ''para''-methoxybenzyl ether. The alcohol is released, and the ''para''-methoxybenzyl ether converts to ''para''-methoxybenzaldehyde. The balanced equation is as follows:
:{{chem2|2 [NH4]2[Ce(NO3)6] + H3COC6H4CH2OR + H2O → 4 NH4+ + 2 Ce(3+) + 12 NO3− + 2 H+ + H3COC6H4CHO + HOR}}

==Other applications==
CAN is also a component of [[chrome plating|chrome]] [[etching (microfabrication)|etchant]],<ref name=CRCCr>{{cite book |title=CRC Handbook of Metal Etchants |url=https://archive.org/details/crchandbookmetal00walk |url-access=limited |last=Walker |first=Perrin |author2=William H. Tarn |year=1991 |pages=[https://archive.org/details/crchandbookmetal00walk/page/n299 287]–291 |isbn=0-8493-3623-6}}</ref> a material that is used in the production of [[photomask]]s and [[liquid crystal display]]s.{{citation needed|date=February 2018}}

==References==
{{reflist}}
<!-- Dead note "3": Budavari, Susan (Ed.). (1989). ''The Merck Index'' (11th ed.). Rahway, NJ: Merck. -->
<!-- Dead note "4": Macintyre, J. E. (Ed.). (1992). ''Dictionary of Inorganic Compounds'' (Vol. 3). London: Chapman & Hall. -->
<!-- Dead note "5": More, Shivaji V.; Sastry, N.V.; Yao, Ching-Fa. "Cerium (IV) Ammonium Nitrate (CAN) as a Catalyst in Tap Water: A Simple, Proficient and Green Approach for the Synthesis of Quinoxalines" ''Green Chemistry'' (2006) volume 1, pp.91-95. -->
<!-- Dead note "6": Wells, A. F. (1984). ''Structural Inorganic Chemistry'' (5th ed.). Oxford, UK: Clarendon Press. -->
<!-- Dead note "7": Connelly, N. G.; Geiger, W. E. "Chemical Redox Agents for Organometallic Chemistry" ''[[Chemical Reviews]]'' (1996), vol. 96, pp.877–910 -->
<!-- Dead note "8": Sridharan, V.; Avendaño, C.; Menéndez, J. C. "CAN-catalyzed three-component reaction between anilines and alkyl vinyl ethers: stereoselective synthesis of 2-methyl-1,2,3,4-tetrahydroquinolines and studies on their aromatization" ''Tetrahedron'' (2007), volume 63, pp. 673–681. -->

==External links==
* [https://www.organic-chemistry.org/chemicals/oxidations/ceriumammoniumnitrate-can.shtm Oxidizing Agents: Cerium Ammonium Nitrate]

{{Cerium compounds}}
{{Ammonium salts}}

[[Category:Ammonium compounds]]
[[Category:Cerium(IV) compounds]]
[[Category:Nitrates]]
[[Category:Coordination complexes]]
[[Category:Oxidizing agents]]
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