| 词条 | Pyridinium chlorochromate |
| 释义 |
| Verifiedfields = changed | Watchedfields = changed | verifiedrevid = 464376959 | Name = Pyridinium chlorochromate | ImageFile = Corey-Reagenz.svg | ImageSize = 150px | ImageName = Chemical structure of pyridinium chlorochromate | ImageFileL1 = Pyridinium-3D-balls.png | ImageNameL1 = Ball-and-stick model of the pyridinium cation | ImageFileR1 = Chlorochromate-3D-balls.png | ImageNameR1 = Ball-and-stick model of the chlorochromate anion | IUPACName = Pyridinium chlorochromate | OtherNames = PCC; Corey-Suggs reagent |Section1={{Chembox Identifiers | CASNo_Ref = {{cascite|changed|??}} | CASNo = 26299-14-9 | ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}} | ChemSpiderID = 10608386 | SMILES = C1=CC=[NH+]C=C1.[O-][Cr](=O)(=O)Cl | StdInChI_Ref = {{stdinchicite|changed|chemspider}} | StdInChI = 1S/C5H5N.ClH.Cr.3O/c1-2-4-6-5-3-1;;;;;/h1-5H;1H;;;;/q;;+1;;;-1 | StdInChIKey_Ref = {{stdinchicite|changed|chemspider}} | StdInChIKey = LEHBURLTIWGHEM-UHFFFAOYSA-N | InChI = 1/C5H5N.ClH.Cr.3O/c1-2-4-6-5-3-1;;;;;/h1-5H;1H;;;;/q;;+1;;;-1/rC5H5N.ClCrO3/c1-2-4-6-5-3-1;1-2(3,4)5/h1-5H;/q;-1/p+1 | InChIKey = LEHBURLTIWGHEM-YOEUSAHMAN }} |Section2={{Chembox Properties | Formula = C5H6ClCrNO3 | MolarMass = 215.56 g/mol | Appearance = yellow-orange solid[1] | MeltingPtC = 205 | SolubleOther = soluble in acetone, acetonitrile, THF | Solvent = other solvents }} |Section7={{Chembox Hazards | ExternalSDS = external SDS | GHSPictograms = {{GHSp|GHS03}}{{GHSp|GHS08}}{{GHSp|GHS07}}{{GHSp|GHS09}} | HPhrases = {{H-phrases|350|272|317|410}} | PPhrases = {{P-phrases|201|280|273|221|308+313|302+352}} | MainHazards = Carcinogenicity, aquatic toxicity | NFPA-F = 1 | NFPA-H = 2 | NFPA-R = 2 | NFPA-S = OX | NFPA_ref = [2] }} }}Pyridinium chlorochromate (PCC) is a yellow-orange salt with the formula [C5H5NH]+[CrO3Cl]-. It is a reagent in organic synthesis used primarily for oxidation of alcohols to form carbonyls. A variety of related compounds are known with similar reactivity. Although no longer widely used,{{Citation needed|date=January 2019}} PCC offers the advantage of the selective oxidation of alcohols to aldehydes or ketones, whereas many other reagents are less selective.[1] Structure and preparationPCC consists of a pyridinium cation, [C5H5NH]+, and a tetrahedral chlorochromate anion, [CrO3Cl]−. Related salts are also known, such as 1-butylpyridinium chlorochromate, [C5H5N(C4H9)][CrO3Cl] and potassium chlorochromate. PCC is commercially available. Discovered by accident,[3] the reagent was originally prepared via addition of pyridine into a cold solution of chromium trioxide in concentrated hydrochloric acid:[4] C5H5N + HCl + CrO3 → [C5H5NH][CrO3Cl] In one alternative method, formation of chromyl chloride (CrO2Cl2) fume during the making of the aforementioned solution was minimized by simply changing the order of addition: a cold solution of pyridine in concentrated hydrochloric acid was added to solid chromium trioxide under stirring.[5] UsesOxidation of alcoholsPCC is used as an oxidant. In particular, it has proven to be highly effective in oxidizing primary and secondary alcohols to aldehydes and ketones, respectively. The reagent is more selective than the related Jones reagent, so there is little chance of over-oxidation to form carboxylic acids as long as water is not present in the reaction mixture. A typical PCC oxidation involves addition of an alcohol to a suspension of PCC in dichloromethane.[6][7][8] The general reaction is: 2 [C5H5NH][CrO3Cl] + 3 R2CHOH → 2 [C5H5NH]Cl + Cr2O3 + 3 R2C=O + 3 H2O For example, the triterpene lupeol was oxidized to lupenone:[9] Other reactionsWith tertiary alcohols, the chromate ester formed from PCC can isomerize via a [3,3]-sigmatropic reaction, the Babler oxidation. Other common oxidants usually lead to dehydration because such alcohols cannot be oxidized directly. PCC also converts suitable unsaturated alcohols and aldehydes to cyclohexenones. This pathway, an oxidative cationic cyclization, is illustrated by the conversion of (−)-citronellol to (−)-pulegone. PCC also effects allylic oxidations, for example, in conversion of dihydrofurans to furanones.[1] Related reagentsOther more convenient or less toxic reagents for oxidizing alcohols include dimethyl sulfoxide, which is used in Swern and Pfitzner–Moffatt oxidations, and hypervalent iodine compounds, such as the Dess–Martin periodinane. SafetyOne disadvantage to the use of PCC is its toxicity, which it shares with other hexavalent chromium compounds. See also
References1. ^1 2 {{cite encyclopedia |last1=Piancatelli |first1= G. |last2=Luzzio |first2=F. A. |encyclopedia=e-EROS Encyclopedia of Reagents for Organic Synthesis |title=Pyridinium Chlorochromate |year=2007 |publisher=John Wiley & Sons |doi=10.1002/9780470842898.rp288.pub2}} 2. ^{{cite web |url=http://www.acros.com/Ecommerce/msds.aspx?PrdNr=18367&Country=US&Language=en |title=Safety Data Sheet |year=2015 |website=Acros Organics |access-date=2016-06-10}} 3. ^{{cite web |url=http://blogs.sciencemag.org/pipeline/archives/2005/10/11/the_old_stuff#44460 |title=The Old Stuff |last=Lowe |first=Derek |author-link=Derek Lowe (chemist) |website=In The Pipeline |publisher=Science |access-date=2015-11-21}} 4. ^{{cite journal |last1=Corey |first1=E. J. |last2=Suggs |first2=J. W. |year=1975 |title=Pyridinium Chlorochromate. An Efficient Reagent for Oxidation of Primary and Secondary Alcohols to Carbonyl Compounds |journal=Tetrahedron Lett. |volume=16 |issue=31 |pages=2647–2650 |doi=10.1016/S0040-4039(00)75204-X}} 5. ^{{cite journal |last1=Agarwal |first1=S. |last2=Tiwari |first2=H. P. |last3=Sharma |first3=J. P. |year=1990 |title=Pyridinium Chlorochromate: An Improved Method for Its Synthesis and Use of Anhydrous Acetic Acid as Catalyst for Oxidation Reactions |journal=Tetrahedron |volume=46 |issue=12 |pages=4417–4420 |doi=10.1016/S0040-4020(01)86776-4}} 6. ^{{OrgSynth | author = Paquette, L. A.; Earle, M. J.; Smith, G. F. | year = 1996 | title = (4R)-(+)-tert-Butyldimethylsiloxy-2-cyclopenten-1-one | volume = 73 | pages = 36 | prep = cv9p0132 | collvol = 9 | collvolpages = 132}} 7. ^{{OrgSynth | author = Tu, Y.; Frohn, M.; Wang, Z.-X.; Shi, Y. | year = 2003 | title = Synthesis of 1,2:4,5-Di-O-isopropylidene-D-erythro-2,3-hexodiulo-2,6-pyranose. A Highly Enantioselective Ketone Catalyst for Epoxidation | volume = 80 | pages = 1 | prep = v80p0001}} 8. ^{{OrgSynth | author = White, J. D.; Grether, U. M.; Lee, C.-S. | year = 2005 | title = (R)-(+)-3,4-Dimethylcyclohex-2-en-1-one | volume = 82 | pages = 108 | prep = v82p0108 | collvol = 11 | collvolpages = 100}} 9. ^{{cite journal |last1=Lao |first1=A. |last2=Fujimoto |first2=Y. |last3=Tatsuno |first3=T. |year=1984 |title=Studies on the Constituents of Artemisia argyi Lévl & Vant |url=https://www.jstage.jst.go.jp/article/cpb1958/32/2/32_2_723/_article |journal=Chem. Pharm. Bull. |volume=32 |issue=2 |pages=723–727 |doi=10.1248/cpb.32.723 |access-date=2016-06-05}} Further reading
External links
4 : Chromates|Oxidizing agents|IARC Group 1 carcinogens|Pyridinium compounds |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。