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Pyridinium chlorochromate

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Pyridinium chlorochromate
Chemical structure of pyridinium chlorochromate
Ball-and-stick model of the pyridinium cation
Ball-and-stick model of the pyridinium cation
Ball-and-stick model of the chlorochromate anion
Ball-and-stick model of the chlorochromate anion
Names
IUPAC name
Pyridinium chlorochromate
Other names
PCC
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.043.253 Edit this at Wikidata
  • InChI=1S/C5H5N.ClH.Cr.3O/c1-2-4-6-5-3-1;;;;;/h1-5H;1H;;;;/q;;+1;;;-1 ☒N
    Key: LEHBURLTIWGHEM-UHFFFAOYSA-N ☒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
    Key: LEHBURLTIWGHEM-YOEUSAHMAN
  • C1=CC=[NH+]C=C1.[O-][Cr](=O)(=O)Cl
Properties
C5H6ClCrNO3
Molar mass 215.56 g/mol
Appearance yellow-orange solid[1]
Melting point 205 °C (401 °F; 478 K)
Solubility in other solvents soluble in acetone, acetonitrile, THF
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Carcinogenicity, aquatic toxicity
GHS labelling:
class="wikitable collapsible" style="min-width: 50em;"
GHS hazard pictograms[2]
Pictogram Code Symbol description Image link
GHS01: Explosive GHS01 {{GHS exploding bomb}} Image:GHS-pictogram-explos.svg Explosive
GHS02: Flammable GHS02 {{GHS flame}} Image:GHS-pictogram-flamme.svg
GHS03: Oxidizing GHS03 {{GHS flame over circle}} Image:GHS-pictogram-rondflam.svg
GHS04: Compressed Gas GHS04 {{GHS gas cylinder}} Image:GHS-pictogram-bottle.svg
GHS05: Corrosive GHS05 {{GHS corrosion}} Image:GHS-pictogram-acid.svg Corrosive
GHS06: Toxic GHS06 {{GHS skull and crossbones}} Image:GHS-pictogram-skull.svg Accute Toxic
GHS07: Exclamation mark GHS07 {{GHS exclamation mark}} Image:GHS-pictogram-exclam.svg Irritant
GHS08: Health hazard GHS08 {{GHS health hazard}} Image:GHS-pictogram-silhouette.svg Health Hazard
GHS09: Environmental hazard GHS09 {{GHS environment}} Image:GHS-pictogram-pollu.svg Environment

See also

GHS hazard pictograms[2]
Pictogram Code Symbol description Image link
GHS01: Explosive GHS01 {{GHS exploding bomb}} Image:GHS-pictogram-explos.svg Explosive
GHS02: Flammable GHS02 {{GHS flame}} Image:GHS-pictogram-flamme.svg
GHS03: Oxidizing GHS03 {{GHS flame over circle}} Image:GHS-pictogram-rondflam.svg
GHS04: Compressed Gas GHS04 {{GHS gas cylinder}} Image:GHS-pictogram-bottle.svg
GHS05: Corrosive GHS05 {{GHS corrosion}} Image:GHS-pictogram-acid.svg Corrosive
GHS06: Toxic GHS06 {{GHS skull and crossbones}} Image:GHS-pictogram-skull.svg Accute Toxic
GHS07: Exclamation mark GHS07 {{GHS exclamation mark}} Image:GHS-pictogram-exclam.svg Irritant
GHS08: Health hazard GHS08 {{GHS health hazard}} Image:GHS-pictogram-silhouette.svg Health Hazard
GHS09: Environmental hazard GHS09 {{GHS environment}} Image:GHS-pictogram-pollu.svg Environment

See also

GHS hazard pictograms[2]
Pictogram Code Symbol description Image link
GHS01: Explosive GHS01 {{GHS exploding bomb}} Image:GHS-pictogram-explos.svg Explosive
GHS02: Flammable GHS02 {{GHS flame}} Image:GHS-pictogram-flamme.svg
GHS03: Oxidizing GHS03 {{GHS flame over circle}} Image:GHS-pictogram-rondflam.svg
GHS04: Compressed Gas GHS04 {{GHS gas cylinder}} Image:GHS-pictogram-bottle.svg
GHS05: Corrosive GHS05 {{GHS corrosion}} Image:GHS-pictogram-acid.svg Corrosive
GHS06: Toxic GHS06 {{GHS skull and crossbones}} Image:GHS-pictogram-skull.svg Accute Toxic
GHS07: Exclamation mark GHS07 {{GHS exclamation mark}} Image:GHS-pictogram-exclam.svg Irritant
GHS08: Health hazard GHS08 {{GHS health hazard}} Image:GHS-pictogram-silhouette.svg Health Hazard
GHS09: Environmental hazard GHS09 {{GHS environment}} Image:GHS-pictogram-pollu.svg Environment

See also

GHS hazard pictograms[2]
Pictogram Code Symbol description Image link
GHS01: Explosive GHS01 {{GHS exploding bomb}} Image:GHS-pictogram-explos.svg Explosive
GHS02: Flammable GHS02 {{GHS flame}} Image:GHS-pictogram-flamme.svg
GHS03: Oxidizing GHS03 {{GHS flame over circle}} Image:GHS-pictogram-rondflam.svg
GHS04: Compressed Gas GHS04 {{GHS gas cylinder}} Image:GHS-pictogram-bottle.svg
GHS05: Corrosive GHS05 {{GHS corrosion}} Image:GHS-pictogram-acid.svg Corrosive
GHS06: Toxic GHS06 {{GHS skull and crossbones}} Image:GHS-pictogram-skull.svg Accute Toxic
GHS07: Exclamation mark GHS07 {{GHS exclamation mark}} Image:GHS-pictogram-exclam.svg Irritant
GHS08: Health hazard GHS08 {{GHS health hazard}} Image:GHS-pictogram-silhouette.svg Health Hazard
GHS09: Environmental hazard GHS09 {{GHS environment}} Image:GHS-pictogram-pollu.svg Environment

See also

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| H272, H317, H350, H410

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| P201, P221, P273, P280, P302+P352, P308+P313

|- | NFPA 704 (fire diamond)

|

[3]
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
2
1
2
OX

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| Safety data sheet (SDS) | external SDS |-



| colspan=2 style="text-align:left; background:#f8eaba; border:1px solid #a2a9b1;" |

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

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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, PCC offers the advantage of the selective oxidation of alcohols to aldehydes or ketones, whereas many other reagents are less selective.[1]

Structure and preparation

PCC 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].

PCC is commercially available. Discovered by accident,[4] the reagent was originally prepared via addition of pyridine into a cold solution of chromium trioxide in concentrated hydrochloric acid:[5]

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.[6]

Uses

Oxidation of alcohols

PCC 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. Unlike with the related Jones reagent, rarely does over-oxidation occur to form carboxylic acids, whether intentionally or accidentally. A typical PCC oxidation involves addition of an alcohol to a suspension of PCC in dichloromethane.[7][8][9] The general reaction is:

2 [C5H5NH][CrO3Cl] + 3 R2CHOH → 2 [C5H5NH]Cl + Cr2O3 + 3 R2C=O + 3 H2O

For example, triterpene lupeol was oxidized to lupenone:[10]

Example of PCC oxidation of secondary alcohol

Other reactions

With 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]

Other 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.

Safety

One disadvantage to the use of PCC is its toxicity, which it shares with other hexavalent chromium compounds.

See also

References

  1. ^ a b c Piancatelli, G.; Luzzio, F. A. (2007). "Pyridinium Chlorochromate". e-EROS Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/9780470842898.rp288.pub2.
  2. ^ a b c d "Globally Harmonized System of Classification and Labelling of Chemicals" (pdf). 2021. Annex 3: Codification of Statements and Pictograms (pp 268–385).
  3. ^ "Safety Data Sheet". Acros Organics. 2015. Retrieved 2016-06-10.
  4. ^ Lowe, Derek. "The Old Stuff". In The Pipeline. Science. Retrieved 2015-11-21.
  5. ^ Corey, E. J.; Suggs, J. W. (1975). "Pyridinium Chlorochromate. An Efficient Reagent for Oxidation of Primary and Secondary Alcohols to Carbonyl Compounds". Tetrahedron Lett. 16 (31): 2647–2650. doi:10.1016/S0040-4039(00)75204-X.
  6. ^ Agarwal, S.; Tiwari, H. P.; Sharma, J. P. (1990). "Pyridinium Chlorochromate: An Improved Method for Its Synthesis and Use of Anhydrous Acetic Acid as Catalyst for Oxidation Reactions". Tetrahedron. 46 (12): 4417–4420. doi:10.1016/S0040-4020(01)86776-4.
  7. ^ Paquette, L. A.; Earle, M. J.; Smith, G. F. (1996). "(4R)-(+)-tert-Butyldimethylsiloxy-2-cyclopenten-1-one". Organic Syntheses. 73: 36{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 9, p. 132.
  8. ^ Tu, Y.; Frohn, M.; Wang, Z.-X.; Shi, Y. (2003). "Synthesis of 1,2:4,5-Di-O-isopropylidene-D-erythro-2,3-hexodiulo-2,6-pyranose. A Highly Enantioselective Ketone Catalyst for Epoxidation". Organic Syntheses. 80: 1{{cite journal}}: CS1 maint: multiple names: authors list (link).
  9. ^ White, J. D.; Grether, U. M.; Lee, C.-S. (2005). "(R)-(+)-3,4-Dimethylcyclohex-2-en-1-one". Organic Syntheses. 82: 108{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 11, p. 100.
  10. ^ Lao, A.; Fujimoto, Y.; Tatsuno, T. (1984). "Studies on the Constituents of Artemisia argyi Lévl & Vant". Chem. Pharm. Bull. 32 (2): 723–727. doi:10.1248/cpb.32.723. Retrieved 2016-06-05.

Further reading

  • Tojo, G.; Fernández, M. (2006). Tojo, G. (ed.). Oxidation of Alcohols to Aldehydes and Ketones: A Guide to Current Common Practice. Basic Reactions in Organic Synthesis. New York: Springer. ISBN 978-0-387-23607-0.
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