Phenols with sodium dichromate

Oxidation of olefinic side chains with ozone to form aromatic aldehydes gives erratic results and therefore other oxidants are employed. For this purpose, the most widely used oxidant is nitrobenzene in dilute alkali the mixture is allowed to react at moderate temperatures for several hours. Thus, hydroxy benzaldehydes may be obtained from propenyl-phenols, which in turn are readily prepared by the Claisen rearrangement of Oalkyl ethers (method 100). Sodium dichromate in the presence of sulfanilic acid, which removes the aldehyde as it is formed, gives yields as high as 86% in the oxidation of isoeugenol and isosafrole. ... 

SODIUM DICHROMATE (10588-01-9) A strong oxidizer. Reacts violently with reducing agents, acids, acetic anhydride, hydrazine, combustible materials, organic substances, metal powders. Reacts with acrolein, antimony trisulfide, antimony tritelluride, arsenic penta-sulfide, 1,1-dichloro-l-nitroethane, 1,3-dichloropropene, diethylamine, fluorine, hydrazine, potassium iodide, sodium tetraborate, sodium tetraborate decahydrate, sodium borohydride, zirconium dusts, j-trioxane. Incompatible with m-bis(trichlormethyl)benzene, hydroxy-lamine. Aqueous solution is caustic incompatible with acids, alcohols, aldehydes, alkylene oxides, cresols, caprolactam solution, epichlorohydrin, organic anhydrides, glycols, maleic anhydride, phenols. Attacks aluminum, copper, brass, bronze, tin, zinc, especially in the presence of moisture. 

The classical method for preparing hydroquinone is based on the oxidation of aniline with manganese dioxide or sodium dichromate in sulfuric acid. The qui-none which is obtained as an intermediate is reduced to hydroquinone with iron filings in dilute hydrochloric acid. This process, which is still used e.g. in India and China, is characterized by the simultaneous production of large amounts of manganese or chromium and iron salts, together with ammonium sulfate. For this reason, oxidative cleavage of p-diisopropylbenzene similarly to phenol synthesis was developed for the production of hydroquinone. 

Production capacity for sodium sulfate, or salt cake, has remained fairly constant over the last decade, with the number of producing plants continuing to decline. Over half of the U.S. supply of Na2S04 is produced from natural brines. Most of the remainder is by-product derived from the production of viscose rayon, sodium dichromate, and sulfonation process phenol. Salt cake produced in the manufacture of HCl from salt by the action of sulfuric acid (Mannheim process), or SO2 and air (Hargreaves process), is on the decline. 

HIDROXILAMINA (Spanish) (7803-49-8) A powerful reducing agent. Aqueous solution is a base. Contact with water or steam causes decomposition to ammonium hydroxide, nitrogen, and hydrogen. Contaminants and/or elevated temperatures above (reported at 158°F/70°C and 265°F/129°C) can cause explosive decomposition. Moisture in air or carbon dioxide may cause decomposition. Violent reaction with oxidizers, strong acids, copper(II) sulfate, chromium trioxide, potassium dichromate, phosphorus chlorides, metals calcium, sodium, zinc. Incompatible with carbonyls, pyridine. Forms heat-sensitive explosive mixtures with calcium, zinc powder, and possibly other finely divided metals. Aqueous solution incompatible with organic anhydrides, acrylates, alcohols, aldehydes, alkylene oxides, substituted allyls, carbonyls, cellulose nitrate, cresols, caprolactam solution, epichlorohydrin, ethylene dichloride, glycols, isocyanates, ketones, nitrates, phenols, pyridine, vinyl acetate. Attacks aluminum, copper, tin, and zinc. 

Epoxy and nitrile-phenolic adhesives have been used to bond these plastics after surface preparation. The surface can be etched with a sodium sulfuric-dichromate acid solution at elevated temperature. Flame treatment and corona discharge have also been used. However, plasma treatment has proven to be the optimal surface process for these materials. Shear strengths in excess of 3000 Ib/in have been reported on polyethylene treated for 10 min in an oxygen plasma and bonded with an epoxy adhesive. Polyolefin materials can also be thermally welded, but they cannot be solvent cemented. 

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