Chromium trioxide CrO

X-3 Chromium trioxide (CrOs ) and acetic anhydride (Ac, O) oxidation. This reaction is good only Tor the formation of aromatic aldehydes. This reaction requires a Cllj attached directly to the aromatic nucleus ... 

In aqueous medium, chromium trioxide (CrOs) exists in equilibrium with several Cr(VI) species such as H2Cr04, Cr207 , H2Cr20y, H2Cr207, Cr04 " and HCr04. The... 

Most other oxidizing agents, such as chromium trioxide (CrOs) in aqueous acid, oxidize primary alcohols to carboxylic acids. An aldehyde is involved as an intermediate in this reaction but can t usually be isolated because it is further oxidized too rapidly. 

Chromium trioxide (CrOs) immobilized on premoistened alumina affords efficient oxidation of benzyl alcohols to carbonyl compounds by simple mixing (Scheme 7). Remarkably, neither the over-oxidation to carboxylic acids nor the formation of tar, a typical occurrence in many CrOs oxidations, is observed. ... 

Analyst (London) 58 335 1933]. Alternatively, successive small portions of KMn04 have been added to acetone at reflux, until the violet colour persists, followed by drying and distilling. Refluxing with chromium trioxide (CrOs) has also been used. Methanol has been removed from acetone by azeotropic distillation (at 35°) with methyl bromide, and treatment with acetyl chloride. 

A reagent that is often used to oxidize alcohols is chromic acid (H2Cr04), which is formed when chromium trioxide (CrOs) or sodium dichromate (Na2Cr207) is dissolved in aqueous acid. These reactions are easily recognized as oxidations because the number of C—H bonds in the reactant decreases and the number of C — O bonds increases. 

Grignard reaction with formaldehyde closer to our desired product. Subsequent hydrolysis will yield 2,2-dimethylbutanol our desired product is 2,2-dimethylbutanal. Oxidation of the primary alcohol to the aldehyde can be accomplished with Sarett s reagent, a combination of chromium trioxide (CrOs) with pyridine. 

B) Chromium, The reduction of green chromic oxide, CraOs, by aluminum does not furnish suflBcient heat in a small crucible to melt the alumina completely. The green oxide is therefore mixed with one-third its weight of chromium trioxide, CrOs. The latter is hygroscopic, but mixing it with the very fine CraOs powder protects it from atmospheric moisture to some extent. 

The crystals are chromium trioxide, CrOs, not chromic acid, H2Cr04. The Shlubility of chromium trioxide in water was measured by R. Kremann who found that sat. soln. at d° contained S grms. of CrOs per 100 grms. of soln. 

Both Cr(III) and Cr(VI) form compounds whose water solubilities range from very high to very low. Many compounds of industrial importance, such as the sodium, potassium, and ammonium chromates and dichromates, chromium trioxide (CrOs), and the hydrated Cr(III) nitrate, chloride. 

Concentrated sulphuric acid (Sg 1.83) Sodium dichromate (Na2Cr207-2H20) [or chromium trioxide (CrOs)]... 

In small-scale reactions, the Jones reagent, which consists of chromium trioxide (CrO in a solution of aqueous acetone and sulfuric acid, is used to oxidize alcohols. The Jones reagent converts primary alcohols to aldehydes and then immediately oxidizes the aldehydes to carboxylic acids. It also converts secondary alcohols to ketones. 

Chromium trioxide is also solublized in dichloromethane in the form of complex chromates Q+[X(CrO,) ] by the addition of an appropriate tetra-n-butylammonium salt [9-14],... 

Safety. The addition of concentrated sulphuric acid on sodium (or potassium) dichromate is to produce chromium trioxide, which is a powerful oxidizing agent capable of oxidizing carbon to carbon dioxide. The solution is loosely called chromic acid, but although true chromic acid H CrO has not been isolated, the aqueous solution contains dichromic acid, The... 

Chromic Acid. (Chromic Anhydride or Chromium Trioxide), [Chrom (Vl)-oxyd in Ger]. CrO, mw 100,01 (The name "chromic acid is in common use, although the true acid l CrO, exists only in soln). Dark purplish-red deliq crysts, mp 197° (dec), d 2.70 at 20° v sol in w sol in ale ether. Solubilities in w at different temps are given in Ref 2a, pl996- Can be prepd by treating Na dichromate with coned... 

Chromium peroxide (CrOs), obtained by the oxidation of chromium trioxide with hydrogen peroxide, reacts with amines forming complexes, like 2,2 -bipyridylchromium (BPCP) and pyridinechromium (PCP) peroxides, that oxidize efficiently alcohols to aldehydes and ketones 426b... 

The typical Phillips catalyst comprises chemically anchored chromium species on a silica support. The formation of a surface silyl chromate, and eventually silyl dichromate [scheme (29)], is significant during the catalyst preparation, because at the calcination temperature chromium trioxide would decompose to lower-valent oxides. Chromium trioxide probably binds to the silica as the chromate initially, at least for the ordinary 1% loading. However, some rearrangement to the dichromate at high temperature may occur. It is incorrect to regard only one particular valence state of chromium as the only one capable of catalysing ethylene polymerisation. On the commercial CrOs/silica catalyst the predominant active species after reduction by ethylene or carbon monoxide [scheme (59)] is probably Cr(II), but other species, particularly Cr(III), may also polymerise ethylene under certain conditions ... 

Two independent syntheses of quadrone eiiq>loyed an allylic oxidation with rearrangement, as shown in equation (3), where the chromium trioxide-(3,5-dimethylpyrazole) reagent (CrOs DMP) was used. In some cases, the success of the reaction strongly depends on the nature of the oxidant, as shown in an iq>proach to (-)-upial (equation 4). Here the chi ium trioxide-heterocycle reagents, which are weaker oxidants, are quite inferior compared to the Fieser reagent ... 

Dark, brownish-red needles, or rhombic prisms, very readily soluble in water. Chromium trioxide contains almost 100 per cent of CrO,. 

SYNONYMS Synonyms of chromates vary depending upon the specific compound. Synonyms of chromic acid (CrOs) are as follows chromic anhydride, chromic oxide, chromium (VI) oxide (1 3) chromium trioxide, monochromium trioxide. 

CrOs. Chromium oxide can also oxidize benzylic positions., as in the Etard reaction (see sec. 3.8.E). When 391 was treated with chromium trioxide in acetic acid, an 85% yield of 392 was obtained, as part of Pan s synthesis of (-)-6,7-dehydrofeiruginyl methyl ether. l... 

CrOg Chromium trioxide, chromic oxide (or anomalously chromic acid), is very stable (61,64). Its magnetic properties have been studied by Datur (65). The CrO anion has no 3d electrons, and its ultraviolet spectra contain intense charge transfer bands (66,67) which have been widely studied both experimentally (67,68) and theoretically (67,69). Its structure was reported by Bystrbm and Wilhelmi (70). 

It is doubtful if hydrated chromium trioxide has been prepared in the solid state. H. Moissan 2 said that if an almost sat. aq. soln. of chromium trioxide be kept for several hrs. at about 90°, and then cooled below 0°, small red crystals of chromic acid, H2Cr04, collect on the walls of the containing vessel. This does not agree with J. J. Berzelius s observations, while F. Mylius and R. Funk, T. Costa, and E. Field were unable to confirm H. Moissan s observation. H. C. Jones showed that the f.p. of aq. soln. of chromium trioxide agreed with the assumption that the solvation for soln. with m mols of Cr03 per litre, can be represented by the mols of water in combination with a mol of CrOs ... 

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