Acid dichromate

Nitrosobenzene may be obtained by the oxidation of P pheiiylhydroxylamine with acid dichromate solution at 0° ... 

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. 

When butenediol is treated with acidic dichromate solution, dehydration and oxidation combine to give a high yield of furan [110-00-9],... 

Cleavage of an alkenoic acid can be carried out with permanganate, a permanganate—periodate mixture, periodate or with nitric acid, dichromate, ozone, or, if the unsaturation is first converted to a dihydroxy compound, lead tetraacetate (71,73). Oxidative ozonolysis is a process for the manufacture of azelaic acid [123-99-9] and pelargonic acid (74). 

We have already noted (Section 4.04.2.1.4(xi)) that alkyl groups on pyrazoles are oxidized with permanganate to carboxylic acids. Silver nitrate and ammonium persulfate transform 4-ethyl-1-methylpyrazole (436) into the ketone (437) (72JHC1373). The best yield was obtained starting with the alcohol (438) and using an acid dichromate solution as oxidizing agent. 

COD Design of treatment plant Legislation and controls Oxidation by acid dichromate... 

Dilute acid permanganate/ acid dichromate, 290-294 perbenzoic acid have also been employed in the aromatization of 3,4-dihydro-j3-carbolines. 

Bichromatldsung, /. dichromate solution, bichromsauer, a. of or combined with dichromic acid, dichromate of. bicyclish, a. bicyclic. 

For oxidation with acid dichromate the picture seems to be quite complex, with... 

The mechanism of oxidation with acid dichromate has been intensely studied. 

Hydrazones of the form ArCH=NNH2 react with HgO in solvents such as diglyme or ethanol to give nitriles (ArCN). Aromatic hydroxylamines (Ar—NH-—OH) are easily oxidized to nitroso compounds (Ar—N=0), most commonly by acid dichromate. ... 

During preparation of acetic acid by acid dichromate oxidation of ethanol according to a published procedure, minor explosions occurred on two occasions after refluxing had been discontinued. This possibly may have involved formation of acetaldehyde (which has an AIT of 140°C) and ingress of air into the reaction vessel as it cooled [1]. Runaway reactions during small scale oxidation of ethanol have apparently been experienced by many teachers, poor initial mixing or starting too cool may be the cause [2],... 

Weliky et al. [154] described a procedure for the determination of both organic and inorganic carbon in a single sample of a marine deposit. Carbonate carbon is determined from the carbon dioxide evolved by treatment of the sample with phosphoric acid the residue is then treated with a concentrated solution of dichromate and sulfuric acid to release carbon dioxide from the organic matter. The carbon dioxide produced at the two stages of the analysis is estimated using a carb on analyser based on the thermal conductivity principle. In addition, total carbon content is determined on another subsample using the dry combustion furnace. This provides a check on the values determined by the phosphoric acid dichromate technique. 

Reagents effecting nitroso to nitro group conversion include nitric acid, acidic dichromate, hydrogen peroxide, permanganate, " chromium trioxide, hypochlorite, ... 

Pipette, using a suitable safety pipette filler, 25 ml acid-dichromate mixture into the flask, fit the cold finger dispenser and slowly turn on the water supply. Place on a hotplate and simmer for 2 h. 

After digesting the soil samples, allow to cool and titrate in the same way. If more than 20 ml of acid-dichromate have been reduced, repeat using less sample. 

If the standardization titration was 26 ml ferrous ammonium sulphate solution, it had reacted with 25 ml acid-dichromate containing 1.668 mmol. If the back-titration of the residual acid-dichromate was 10 ml ferrous ammonium sulphate solution, then the residual acid-dichromate amounted to 10 x 1.668/26 = 0.642 mmol. The amount used to oxidize the organic carbon is therefore... 

The mechanism of oxidation with acid dichromate has been intensely studied.98 The currently accepted mechanism is essentially that proposed by Westheimer." The first two steps constitute an example of category 4 (p. 1160). 

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