Chromyl chloride alcohol oxidation

Nitrobenzaldehyde has been prepared from />-nitrotoluene by treatment with isoamyl nitrite in the presence of sodium methylate,1 by oxidation with chromyl chloride,2 cerium dioxide,3 or chromium trioxide in the presence of acetic anhydride.4 It can also be prepared by the oxidation of -nitrobenzyl chloride,5 7>-nitrobenzyl alcohol,6 or the esters of -nitrocinnamic acid.7... 

Oxidation, of primary alcohols to aldehydes, 52, 5 of terminal olefins with chromyl chloride, 51, 6 of 2,4,4-trimethyl-1-pentene with chromyl chloride, 51, 4 with chromium trioxide-pyridine complex, 52, 5... 

Chromyl chloride adsorbed on silica-alumina oxidizes alcohols to aldehydes and ketones.430... 

The coordinative and/or dissociative adsorption of various probe molecules has been used to characterize the surface properties of Ti02) which finds applications as a catalyst, photocatalyst, and sensor. Among the molecules used as probes, we mention CO (37, 38, 563-576), C02 (563, 565, 577), NO (578,579), water (580,581), pyridine (582,583), ammonia (584,585), alcohols (586, 587), ethers (including perfluoroethers) (588), ozone (589), nitrogen oxide (590), dioxygen (591), formic acid (592-594), benzene (584), benzoic acid (595), and chromyl chloride (596). 

Oxidation of alcohols typically proceeds in 4-12 h giving excellent yields of carbonyl products. Chromyl chloride, C1O2CI2, like other Cr species, is a vigorous oxidant of organic compounds. It may be, however, tamed as a silica gel adsoibate. This reagent combination is also a good oxidant of alcohols, alkenes and alkynes, that will tolerate halides, esters, lactones, ethers and nitriles. The shelf life of the reagent t pears to be indefinite in the diy state. 

Chromyl chloride, Cr202Cl2, a dark-red liquid (mp -96.5 °C, bp 117 °C, d 1.911), is prepared from chromium trioxide or sodium dichromate, hydrochloric acid, and sulfuric acid [665]. The reagent is used in solutions in carbon disulfide, dichloromethane, acetone, tert-butyl alcohol, and pyridine. Oxidations with chromyl chloride are often complicated by side reactions and do not always give satisfactory yields. The mechanism of the oxidation with chromyl chloride, the Etard reaction, is probably of free-radical nature [666]. Complexes of chromyl chloride with the compounds to be oxidized have been isolated [666, 667, 668]. 

The reaction of chromyl chloride with alkenes gives epoxides, chlo-rohydrins, chloroketones, and ketones [668, 667, 668, 669, 670] or aldehydes (in the presence of zinc) [671, 672]. Benzene homologues are oxidized to aldehydes [667, 668] or ketones [666, 668, 673], Primary alcohols are converted into aldehydes [674, 675], and trimethylsilyl ethers of enols are transformed into a-hydroxy ketones [676]. 

Other oxidants of hexavalent chromium are chromyl chloride and di-/er/-butyl chromate. Chromyl chloride adsorbed on alumina-silica gel from its solution in dichloromethane oxidizes aliphatic and aromatic alcohols at room temperature within hours in 77-100% yields [675]. Di-tert-butyl chromate, prepared in situ from chromyl chloride in tert-butyl alcohol at -70 °C, gives comparable results under similar conditions [674. Di-tert-butyl chromate, prepared from chromium trioxide and tert-butyl alcohol, oxidizes primary aliphatic and aromatic alcohols to the corresponding aldehydes even at low temperatures (1-2 °C) [677, 678]. 

CHROMYL CHLORIDE (14977-61-8) A powerful oxidizer. Violent reaction with water, producing hydrochloric and chromic acids, and chlorine gas. Potentially violent and explosive reaction with reducing agents, acetone, alcohols, calcium sulfide, combustible materials, gaseous or liquid ammonia, ethers, nonmetal halides, fuels, nonmetal hydrides, fluorine. 

This chromyl chloride based reagent is inferior to Collins reagent for oxidation of allylic alcohols since cis-trans isomerization occurs. It has also been found to be unsatisfactory for oxidation of m-hydroxybenzyl alcohol (38%... 

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