Chromic acids

Alternatives.4 Fortunately, there are a variety of alternatives to chromic acid, so its use is really unnecessary. Some homemade alternatives include  

Combining H2O2 and H2S04 to make peroxysulfuric acid. This solution 

a solution of three parts sulfuric acid to one part nitric acid. 

Eosulf (Micro, International Products Corporation) contains EDTA (an 

Phosphate-based cleaning solutions do very well as surfactants, and 

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Oxidation with chromic acid gives 4-benzoquinone. 

An optically active, secondary terpene alcohol. ( —)-Piperilol is found in various eucalyptus oils and (-l-) piperitol in the oil from a species of Andropogon. A somewhat viscous oil of pleasant smell. It yields piperitone on oxidation with chromic acid. 

Sheet aluminium can be given a colour by a similar process. The aluminium is first made the anode in a bath of chromic acid (p. 377) when, instead of oxygen being evolved, the aluminium becomes coated with a very adherent film of aluminium oxide which is very adsorbent. If a dye is added to the bath the oxide film is coloured, this colour being incorporated in a film which also makes the remaining aluminium resistant to corrosion. This process is called anodising aluminium. 

Chromium(VI) oxide is very soluble in water initially, chromic acid , H2Cr04, may be formed, but this has not been isolated. If it dissociates thus ... 

Chromatographic Separation of a Mixture of o- and p-Nitroaniline. Prepare a glass tube A (Fig. 24) in which the wider portion has a diameter of 3 cm. and a length of ca. 30 cm. the narrow portion at the base has a diameter of 5-7 mm. Wash the tube thoroughly (if necessary, with chromic acid, followed by distilled water and ethanol) and then dry. Insert a small plug of cotton-wool P as shown just within the narrow neck of the tube it is essential that this plug does not project into the wider portion of the tube. Clamp the tube in a vertical position. 

The most widely used cleansing agent is the chromic acid cleaning mixture. It is essentially a mixture of chromic acid (CrOj) and concentrated sulphuric acid, and possesses powerful oxidising and solvent properties. Two methods of preparation are available —... 

CAUTION. Ethers that have been stored for long periods, particularly in partly-filled bottles, frequently contain small quantities of highly explosive peroxides. The presence of peroxides may be detected either by the per-chromic acid test of qualitative inorganic analysis (addition of an acidified solution of potassium dichromate) or by the liberation of iodine from acidified potassium iodide solution (compare Section 11,47,7). The peroxides are nonvolatile and may accumulate in the flask during the distillation of the ether the residue is explosive and may detonate, when distilled, with sufficient violence to shatter the apparatus and cause serious personal injury. If peroxides are found, they must first be removed by treatment with acidified ferrous sulphate solution (Section 11,47,7) or with sodium sulphite solution or with stannous chloride solution (Section VI, 12). The common extraction solvents diethyl ether and di-tso-propyl ether are particularly prone to the formation of peroxides. 

Benzoquinone ( quinone ) is obtained as the end product of the oxidation of aniline by acid dichromate solution. Industrially, the crude product is reduced with sulphur dioxide to hydroquinone, and the latter is oxidised either with dichromate mixture or in very dilute sulphuric acid solution with sodium chlorate in the presence of a little vanadium pentoxide as catalyst. For the preparation in the laboratory, it is best to oxidise the inexpensive hydroquinone with chromic acid or with sodium chlorate in the presence of vanadium pent-oxide. Naphthalene may be converted into 1 4-naphthoquinone by oxidation with chromic acid. 

The allyiic oxidation with derivatives of chromic acid (K.B. Wiberg, 1965 H.G. Boscbe, 1975), c.g. di-/-butyl chromate (K. Fujita, 1961), CrOj/pyridine (W.O. Dauben, 1969), or KjCrO (C.Y. Cuiileron, 1970), gives similar products in occasionally very high yields. 

Thus 2-phenyl-4(hydroxymethyl) thiazole upon oxidation with aqueous chromic acid yields 2-phenyl-4-thiazolecarboxylic acid (25,26). 

Thiazolecarboxaldehydes are very easily oxidized to carboxylic acids by most oxidizing agents, the most common being KMn04 in cold pyridine or boiling acetone. Thiazolecarboxylic acids are obtained in 50% yield (29). Other oxidizing agents such as Ag 0 in dioxane and water (29, 103), chromic acid, and so forth are also used. 

On the other hand an alkyl side chain on a benzene nng is oxidized on being heated with chromic acid The product is benzoic acid or a substituted derivative of benzoic acid... 

An alternative oxidizing agent similar to chromic acid in Its reactions with or game compounds is potas Slum permanganate (KMn04)... 

Chromic acid oxidation of 4 tert butyl 1 2 dimethylbenzene... 

A compound was obtained from a natural product and had the molecular formula C14H20O3 It contained three methoxy (—OCH3) groups and a —CH2CH=C(CH3)2 substituent Oxidation with either chromic acid or potassium permanganate gave 2 3 5 trimethoxybenzoic acid What is the structure of the compound" ... 

Pellagra is a disease caused by a deficiency of niacm (C6FI5NO2) in the diet Niacin can be synthesized in the laboratory by the side chain oxidation of 3 methylpyndine with chromic acid or potassium permanganate Suggest a reasonable structure for niacin... 

Chromic acid (H2Cr04) is a good oxidizing agent and is formed when solutions containing chromate (Cr04 ) or dichromate (Cr207 ) are acidified Sometimes it is possible to obtain aldehydes m satisfactory yield before they are further oxidized but m most cases carboxylic acids are the major products isolated on treatment of primary alco hols with chromic acid... 

Step 1 Reaction of the alcohol with chromic acid gives an alkyl chromate... 

Oxidation of secondary alcohols to ke tones (Section 15 10) Many oxidizing agents are available for converting sec ondary alcohols to ketones PDC or PCC may be used as well as other Cr(VI) based agents such as chromic acid or po tassium dichromate and sulfuric acid... 

A primary or secondary alkyl side chain on an aromatic ring is converted to a carboxyl group by reaction with a strong oxidizing agent such as potassium permanga nate or chromic acid... 

Oxidation of primary alcohols (Section 15 10) Potassi um permanganate and chromic acid convert primary al cohols to carboxylic acids by way of the corresponding aldehyde... 

Oxidation of aldehydes (Section 17 15) Aldehydes are particularly sensitive to oxidation and are converted to carboxylic acids by a number of oxidizing agents in eluding potassium permanganate and chromic acid... 

The structure of the bicychc monoterpene borneol is shown in Figure 26 7 Isoborneol a stereoisomer of borneol can be prepared in the labora tory by a two step sequence In the first step borneol is oxidized to camphor by treatment with chromic acid In the second step camphor is reduced with sodium borohydride to a mixture of 85% isoborneol and 15% borneol On the basis of these transformations deduce structural formulas for isoborneol and camphor... 

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