Chromic oxide complexes with pyridine

Most allylic oxidations of methylene to carbonyl groups are carried out by chromic oxide [552, 555] or its complexes with pyridine [593, 606] and performed on steroidal esters [552, 593, 606] and ketones [61, 552] (equation 130). 

Oxetanol can be oxidized to 3-oxetanone in fair yield by means of the chromic oxide-pyridine complex. This ketone reacts with base in an unknown manner and polymerizes on standing. 

Magnanini studied the absorption spectrum and A. Speransky found that the electrical conductivity of aq. soln. shows that only a small proportion of the salt is ionized. The soln. of the violet modification conducts electricity three times better than that of the green. G. Gore electrolyzed a cone. soln. of chromic fluoride acidified with hydrofluoric and hydrochloric acids, and found that the liquid became hot no gas was liberated at the cathode, but chlorine and ozone were liberated at the platinum anode which was not corroded. C. Poulenc showed that the salt is reduced by hydrogen at dull redness. The heat of formation is 230-95 Cals, per mol—vide infra, the dichloride. Steam transforms chromic fluoride into chromic oxide. Chromic fluoride is insoluble in water, and alcohol hydrogen chloride transforms it into chromic chloride hot hydrochloric, sulphuric, and nitric acids attack chromic fluoride only a little hydrogen sulphide converts it into black sulphide and molten alkali nitrate or carbonate converts it into chromate. A. Costachescu prepared complex pyridine salts. 

The complex of pyridine with chromic anhydride, Cr03 2G5H5N, which in the crystalline form may be di- or polymeric i , is a useful oxidizing agent i . ... 

The oxidation of primary alcohols using chromic acid, chromic oxide-pyridine complex, manganese dioxide, etc., gives aldehydes in good yields. Allylic alcohols are readily oxidized at room temperature with active manganese dioxide. 

Aldehydes are further oxidized to carboxylic acids, RCOOH. To get aldehydes, milder reagents, such as the Jones (diluted chromic acid in acetone) or Collins reagent (a complex of CrOj with 2 mol of pyridine), are used. 

Oxidation of O-methyldeacetyllythramine (75) with chromic anhydride-pyridine complex yielded the ketone (79) which exchanged four hydrogens on treatment with sodium deuteroxide in deuterium oxide and deutero-methanol (12). 

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