Pyridinium dichromate

Description

Palladium on carbon (Pd/C) is a common catalyst for hydrogenation and/or hydrogenolysis of various functional groups. It is typically purchased as a black powder which is 5% or 10% palladium (by wt%) adsorbed on carbon. The reagent is normally purchased dry or as a solid which is 50% wet with water. The 50% wet with water reagent is the safer to handle option.

Description

Pyridinium dichromate (PDC) is a strong oxidizing agent. It is able to convert primary alcohols to aldehydes, and secondary alcohols to ketones. Because of the associated toxicity of the reagent it is currently rarely used.

Chemical properties

Orange solid

The Uses of Pyridinium dichromate

Pyridinium dichromate (PDC) is an orange colored solid used as an oxidizing agent.
Oxidizing agent for conversion of primary alcohols to aldehydes and ketones, acetals to esters, and didehydroketones to enones in the presence of tert-butyl hydroperoxide.
Pyridinium Dichromate may be used as an alternative to PCC in nucleoside and carbohydrate oxidation, particularly for fragile molecules. PDC can also be used in conjunction with tertbutylhydroperoxide for a variety of oxidative transformations.

The Uses of Pyridinium dichromate

A mixture of the SM (7.2 g, 26.2 mmol) and 10% Pd/C (2 g) in MeOH (100 mL) was stirred under an atmosphere of H2 (50 psi) at RT for 12 h. The mixture was filtered through celite and the filtrate was concentrated. The residue was purified by silica gel flash chromatography to provide the product. [5.8 g, 80%]

The Uses of Pyridinium dichromate

Pyridinium dichromate acts as a strong oxidizing agent used in the conversion of primary alcohols and secondary alcohols to aldehydes and ketones respectively. It plays an important role in the oxidation of unsaturated tertiary alcohols, silyl ethers, the carbon-boron bond, and oximes. Further, it is used in the conversion of acetals to esters and didehydroketones to enones in the presence of tert-butyl hydroperoxide.

Preparation

Pyridinium dichromate can be obtained by gradual addition of a solution of chromic anhydride (Cr2O3) in water to pyridine in ice cold conditions.

Definition

ChEBI: Pyridinium dichromate is a pyridinium salt that is the dipyridinium salt of dichromic acid. It is a strong oxidizing agent which can convert primary and secondary alcohols to aldehydes and ketones respectively. It has a role as an oxidising agent. It contains a dichromate(2-).

Flammability and Explosibility

Flammable

Purification Methods

Dissolve it in the minimum volume of H2O and add 5 volumes of cold Me2CO and cool to -20o. After 3hours the orange crystals are collected, washed with a little cold Me2CO and dried in a vacuum. It is soluble in dimethylformamide (0.9g/mL at 25o), and in H2O, and has a characteristic IR with max at 930, 875, 765, 730 and 730 cm-1. [Corey & Schmidt Tetrahedron Lett 399 1979, Coats & Corrigan Chem Ind (London) 1594 1969.] (Possible CARCINOGEN.) § Available commercially on a polymer support.