Dichromate - Sulfuric Acid Reagent

D. Dichromate-Sulfuric Acid Reagent is prepd by dissolving 0.5g of K2Cr207 in 100ml of 60% sulfuric acid. It was proposed by Oven-ston for use in chromatographic analysis of propints, for the location of substituted ureas and urethanes which have been employed as stabilizers and plasticizers(Ref 18a)... 

In its simplest form, a breath alcohol screening test consists of a sealed glass tube containing a potassium dichromate-sulfuric acid reagent impregnated on silica gel. To administer the test, the ends of the tube are broken off, a mouthpiece is fitted to one end, and the other end is inserted into the neck of a plastic bag. The person being tested then blows into the mouthpiece until the plastic bag is inflated. 

Potassium Dichromate-Perchloric Acid-Nitric Acid-Sulfuric Acid Reagent... 

Sulfo and nitro substituents also often make it harder to degrade the side chain. For the preparation of nitrobenzoic acids from nitrotoluenes a dichromate-sulfuric acid mixture is superior to chromic acid alone in glacial acetic acid trinitrotoluene is converted into trinitrobenzoic acid by the former but is not attacked by the latter reagent. o-Toluenesulfonamide (obtained from the acid by way of the chloride) is oxidized by alkaline permanganate solution... 

An unknown organic liquid, compound A, was found to bum with a yellow, sooty flame and give a positive Lucas test ( 5 min). Upon treatment with sodium dichromate-sulfuric acid solution it produced compound B, which also burned with a yellow, sooty flame. Compound B gave a positive 2,4-dinitrophenylhydrazine test, but a negative result when treated with the Tollens reagent. However, compound B did give a positive iodoform test. 

The consumption of the oxime can be checked by thin-layer chromatography on silica gel G with the solvent system chloro-form/methanol (95/5 v/v) and a spray reagent consisting of 5% potassium dichromate in 40% sulfuric acid. The oxime appears as an immediate dark spot and the aziridine as a yellow spot. The checkers observed identical mobilities (Rf 0.8) for both compounds. 

Ovenston(Ref 5 6) described the chromotographic method of detng carbazole in expls and propints. As the streak reagent, he used a 0.5% soln of K dichromate in 60% sulfuric acid which causes carbazole to turn green. A paperchromatographic detn of carbazole is described in Addnl Ref 1... 

Oxidation of 1-hexanol with chromic acid (sodium or potassium dichromate in aqueous sulfuric acid) yields hexanoic acid. Use of PDC or PCC in dichloromethane is not acceptable because those reagents yield aldehydes on reaction with primary alcohols. 

A number of materials,10 water, certain organic acids, the most important of which is citric acid, and certain inorganic salts, interfere with the determination. The decarboxylation cannot be conducted in the presence of nitrates and when carbonates are present two separate determinations of carbon dioxide are necessary. The procedure is also inapplicable when oxidizing compounds which are soluble in the hot reagent are present. Another interfering substance, sulfur dioxide,01 can be eliminated by the use of a saturated, acidified (sulfuric acid) solution of potassium dichromate to wash the gases evolved by the decarboxylation procedure. 

The chromic acid reagent is prepared by dissolving sodium dichromate (Na2Cr207) in a mixture of sulfuric acid and water. The active species in the mixture is probably chromic acid, H2Cr04, or the acid chromate ion, HC1O4. Adding chromium trioxide (C1O3) to dilute sulfuric acid achieves the same result. 

Sodium dichromate in sulfuric acid ( chromic acid, H2Cr04) is the traditional laboratory reagent for oxidizing secondary alcohols to ketones. Bleach (NaOCl) is an inexpensive, chromium-free alternative that also oxidizes secondary alcohols to ketones. Primary alcohols are usually over-oxidized to carboxylic acids under these conditions. 

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