Pyridinium chlorochromate

Pyridinium chlorochromate

Names
IUPAC name Pyridinium chlorochromate
Other names PCC
Identifiers
CAS Number	26299-14-9 N
3D model (Jmol)	Interactive image
ChemSpider	10608386 N
ECHA InfoCard	100.043.253
InChI 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
SMILES C1=CC=[NH+]C=C1.[O-][Cr](=O)(=O)Cl
Properties
Chemical formula	C5H6ClCrNO3
Molar mass	215.56 g/mol
Appearance	yellow-orange solid
Melting point	205 °C (401 °F; 478 K)
Solubility in other solvents	soluble in acetone, acetonitrile, THF
Hazards
Main hazards	Carcinogenicity, aquatic toxicity
Safety data sheet	external SDS
GHS pictograms
GHS hazard statements	H350, H272, H317, H410
GHS precautionary statements	P201, P280, P273, P221, P308+313, P302+352
R-phrases	R49, R8, R43, R50/53
S-phrases	S53, S45, S60, S61
NFPA 704	1 2 2 OX
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

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.

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, the reagent was originally prepared via addition of pyridine into a cold solution of chromium trioxide in concentrated hydrochloric acid:

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.

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. The general reaction is: