Potassium dichromate production

Pyridine carboxamide [98-92-0] (nicotinamide) (1) and 3-pyridine carboxylic acid [59-67-6] (nicotinic acid) (2) have a rich history and their early significance stems not from their importance as a vitamin but rather as products derived from the oxidation of nicotine. In 1867, Huber prepared nicotinic acid from the potassium dichromate oxidation of nicotine. Many years later, Engler prepared nicotinamide. Workers at the turn of the twentieth century isolated nicotinic acid from several natural sources. In 1894, Su2uki isolated nicotinic acid from rice bran, and in 1912 Funk isolated the same substance from yeast (1). 

In view of its possible interest as the mode of formation of harman, harmine and harmaline in plants, Kermack, Perkin and Robinson investigated the conversion of tryptophan (II) into harman (I) and nor-harman (IV). The latter is produced when tryptophan is condensed with formaldehyde in presence of dilute sulphuric acid and the product (III) oxidised by potassium dichromate. Harman is formed when formaldehyde in this process is replaced by acetaldehyde. 

Struxine, C2iH3(,04N2, obtained by Schaefer from deteriorated nux-vomica seeds in about 0-1 per cent, yield, is regarded as a decomposition product of strychnine or brucine. It forms rhombic crystals from alcohol, is colourless, but becomes yellow on exposure to light and chars at 250°. It yields normal and acid salts, the latter only from excess of acid. With sulphuric acid it gives no coloration, but addition of potassium dichromate produces a yellow colour changing to green. 

The synthetical experiments started by Openshaw and Robinson have for their immediate objective the preparation of one of the possible degradation products of strychnine, and a beginning has been made by the preparation of the lactam of hexahydrocarbazole-1 ll-/SjS -dipropionic acid (XXIV), which reproduces a portion of the strychnine molecule as represented in Robinson s formula (Ilia, p. 574), and in sulphuric acid gives a purple colour with a trace of potassium dichromate (Otto reaction). 

Mention should be made of one of the earliest internal indicators. This is a 1 per cent solution of diphenylamine in concentrated sulphuric acid, and was introduced for the titration of iron(II) with potassium dichromate solution. An intense blue-violet coloration is produced at the end point. The addition of phosphoric(V) acid is desirable, for it lowers the formal potential of the Fe(III)-Fe(II) system so that the equivalence point potential coincides more nearly with that of the indicator. The action of diphenylamine (I) as an indicator depends upon its oxidation first into colourless diphenylbenzidine (II), which is the real indicator and is reversibly further oxidised to diphenylbenzidine violet (III). Diphenylbenzidine violet undergoes further oxidation if it is allowed to stand with excess of dichromate solution this further oxidation is irreversible, and red or yellow products of unknown composition are produced. 

A sensitive spectrophotometric method was reported for the determination of niclosamide and some other antiamebic and anthelmintic drugs either in pure form or in formulations. The method was based on reduction with Zn and HC1 followed by reaction with metol and potassium dichromate at pH 3.0 to give a colored product having maximum absorbance at 530 nm for niclosamide [54]. 

Identify the alcohols, in your answers to Question 10, that would undergo oxidation when heated under reflux with a solution of potassium dichromate (VI) in dilute sulphuric acid. Give the structural formula of the final organic product of the reaction in each case. (6)... 

Adogen has been shown to be an excellent phase-transfer catalyst for the per-carbonate oxidation of alcohols to the corresponding carbonyl compounds [1]. Generally, unsaturated alcohols are oxidized more readily than the saturated alcohols. The reaction is more effective when a catalytic amount of potassium dichromate is also added to the reaction mixture [ 1 ] comparable results have been obtained by the addition of catalytic amounts of pyridinium dichromate [2], The course of the corresponding oxidation of a-substituted benzylic alcohols is controlled by the nature of the a-substituent and the organic solvent. In addition to the expected ketones, cleavage of the a-substituent can occur with the formation of benzaldehyde, benzoic acid and benzoate esters. The cleavage products predominate when acetonitrile is used as the solvent [3]. 

Take the total amount of succinaldehyde (obtained from 4 of the above syntheses combined) and without further treatment or purification (this had better be 15.5 g of succindialdehyde) put into an Erlenmeyer flask of 4-5 liters capacity. Add 21.6 g of methylamine hydrochloride, 46.7 g of acetonedicarboxylic acid, and enough water to make a total volume of 2 liters. Adjust the pH to 8-10 by slowly adding a saturated solution of disodium phosphate. The condensate of this reaction (allow to set for about 6 days) is extracted with ether, the ethereal solution is dried over sodium sulphate and distilled, the product coming over at 113° at 25 mm of pressure is collected. Upon cooling, 14 g of tropinone crystallizes in the pure state. Tropinone can also be obtained by oxidation of tropine with potassium dichromate, hut I could not find the specifics for this operation. 

Small quantities of hazardous solid wastes (such as potassium dichromate, lead nitrate, silver nitrate, asbestos, etc.), liquid chemicals (such as chloroform, PCB, methylene chloride, etc.), petrochemicals (such as gasoline. No. 2 fuel oil, etc.), or pure metals (such as mercury, sodium, etc.), which are stored in bottles or cans, however, are not considered to be hazardous household products. Accordingly these nonhousehold hazardous solid wastes, even in small quantities, can only be properly disposed of by licenced or certified environmental professionals. 

Also, the compound may be obtained as an intermediate in the production of potassium dichromate. The product, however, contains trace amounts of potassium sulfate which is difficult to separate. 

Oxidation of 6-methylphenanthridines with potassium dichromate in acetic acid results in oxidative loss of the methyl group, the product being the phenanthridone (e.g. 67 Scheme 62) (61JCS3771). If a second methyl group is present it remains unchanged. Selenium dioxide oxidizes the 6-methyl group to the aldehyde. 

Potassium Dichromate — Fire Hazards Flash Point (deg. F) Not flammable Flammable Limits in Air (Ho) Not flammable Fire Extinguishing Agents Flood the spill area with water Fire Extinguishing Agents Not to be Used Not pertinent Special Hazards of Combustion Products Not... 

Volumetric Estimation.—Tellurium may be determined by oxidation from the tellurous to the telluric condition, using an excess of potassium dichromatc or permanganate and subsequently titrating the excess of oxidising agent with a standard solution of a suitable reducing agent.2 In order to obtain accurate results with the potassium dichromate titration, certain very definite steps in the procedure are essential, and it is necessary to control the course of the reaction, since hydrochloric and telluric acids interact with production of chlorine. 

Lead azide is dissolved by an aqueous solution of ammonium acetate, but it is not destroyed by it. The solution contains azide ions and lead ions, the latter quantitatively precipitable as lead chromate, PbCr04, by the addition of potassium dichromate solution. Lead azide in aqueous suspension is oxidized by ceric sulfate with the quantitative production of nitrogen gas which may be collected in an azotometer and used for the determination of the azide radical. 

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