Zinc dichromate oxidation

The oxidation of alcohols with metal dichromates, other than sodium or potassium dichromate, has been little explored. Hydrated zinc dichromate (ZnCr207 3H20)367 368a and ferric dichromate [Fe2(Cr207)3],368b—which are very easy to prepare as stable solids—are able to oxidize alcohols in organic solvents.368 Zinc dichromate is particularly efficient in the transformation of a-hydroxyphosphonates into a-ketophosphonates.369... 

Permanganate and dichromate are among our earliest titrimetric reagentspermanganate was introduced in 1846 by Margueritte, and dichromate independently by Schabus and by Penny in 1850. They were used for the titration of iron(II) produced by reduction with zinc. Both oxidants arc strong, E° values for the half-reactions in acid solution being ... 

Tungsten hexafluoride, WF (mp 2.5 °C, bp 17 °C) [529], resembles M0F5 and M0OCI3 in its oxidative properties. However, less exotic reagents such as ozone, ammonium cerium sulfate, or zinc dichromate may be used for a similar purpose. 

Zinc dichromate tiihydrate, ZnCr207<3H20, is obtained as an orange-red solid by adding zinc carbonate to a cold solution of chromium trioxide in dilute sulfuric acid [660]. The applications are oxidations of acetylenes lo a-diketones, of aromatic hydrocarbons to quinones, of alcohols to aldehydes, and of ethers to esters and the oxidative regeneration of carbonyl compounds from their oximes [660]. 

Diarylacetylenes are converted in 55-90% yields into a-diketones by refluxing for 2-7 h with thallium trinitrate in glyme solutions containing perchloric acid [413. Other oxidants capable of achieving the same oxidation are ozone [84], selenium dioxide [509], zinc dichromate [660], molybdenum peroxo complex with HMPA [534], potassium permanganate in buffered solutions [848, 856, 864,1117], zinc permanganate [898], osmium tetroxide with potassium chlorate [717], ruthenium tetroxide and sodium hypochlorite or periodate [938], dimethyl sulfoxide and iV-bromosuccin-imide [997], and iodosobenzene in the presence of a ruthenium catalyst [787] (equation 143). 

Not very many other chromium compounds are suitable for the preparation of carboxylic acids from alcohols. One such compound is zinc dichromate, which oxidizes benzyl alcohol to benzoic acid in 90% yield in dichloromethane solution at room temperature [660]. 

By far the most important oxidation of ethers is their conversion into esters and lactones. Only a few reagents are capable of such a transformation ozone [110], chromium trioxide [539, 586], zinc dichromate [660], potassium permanganate [855], zinc permanganate [898], benzyltriethylam-monium permanganate [902], and ruthenium tetroxide (which gives the best yields) [774, 940] (equations 324 and 325). 

Steroid ketoxides of types (1) and (3), both of which result on dichromate oxidation of A -cholestenyl acetate, are reduced by zinc dust and acetic acid to the corresponding conjugated ketones, (2) and (4). ... 

Zinc metal can be determined in zinc oxide by means of indirect methods. Zinc is oxidized with dichromate (in an H2SO4 or H3PO4 medium), and then the unreacted part of Cr(VI) is determined with 1,5-diphenylcarbazide [106]. In another version, the sample is dissolved in dil. sulphuric acid in the presence of Fe(III) and 1,10-phenanthroline. The red Fe(n)-phen complex is equivalent to the content of Zn in the zinc oxide studied [107]. 

Firouzabadi, H., Iranpoor, N., Sobhani, S., and Sardarian, A.R., High yield preparation of a-keto-phosphonates by oxidation of a-hydroxyphosphonates with zinc dichromate trihydrate (ZnCr2O7 SHjO) under solvent-free conditions. Tetrahedron Lett., 42, 4369, 2001. 

ZINC DICHROMATE (14018-95-2) An oxidizer. Reacts with reducing agents, alcohols, combustible materials, ethers, hydrazines, organic substances, metal powders. 

Both alcohols and aldehydes can be oxidised to carboxylic acids using ruthenium tetroxide an efficient, two-phase (CCl4-aq.NaCl) electro-oxidation method has been developed for the generation of RuO which could be especially useful for oxidations of carbohydrate derivatives, partly protected as acetonides.5 Zinc dichromate... 

Zinc chromates group Zinc oxides and hydroxides group Zinc sulfides group Aurichalcite Cadmium zinc sulfide Claraite Cobalt zinc oxide Copper zinc carbonate, rosasite type Franklinite Iron zinc oxide Iron zinc oxide Lead antimony zinc oxide Matraite Rosasite Smithsonite Sphalerite Wurtzite Zinc carbonate Zinc carbonate hydroxide Zinc dichromate hydrate Zinc hexacyanoferrate(II) Zinc oxide Zinc oxide sulfide Zinc phosphate Zinc potassium chromate Zinc potassium chromate hydrate Zinc sulfate Zinc sulfide Zinc sulfide hydrate Zinc titanate Zincite Blende Mosaic gold Murexide Bieganska et al. (1988) Merck Index (1996)... 

Copper chromate oxide hydrate Cobalt chromate Iron dichromate Iron chromate hydroxide Manganese chromate hydrate Silver chromate Thallium chromate Titanium chromate Cadmium chromate Cadmium chromate hydroxide Mercury chromate Zinc dichromate hydrate Zinc chromate(VI) hydroxide Zinc sodium chromate Zinc potassium chromate... 

Hydrazine Alkali metals, ammonia, chlorine, chromates and dichromates, copper salts, fluorine, hydrogen peroxide, metallic oxides, nickel, nitric acid, liquid oxygen, zinc diethyl... 

Hydroxylamine Barium oxide and peroxide, carbonyls, chlorine, copper(II) sulfate, dichromates, lead dioxide, phosphorus trichloride and pentachloride, permanganates, pyridine, sodium, zinc... 

Sihcon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between sihcon carbide and a variety of compounds at relatively high temperatures. Sodium sihcate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal sihcide. Sihcon carbide decomposes in fused alkahes such as potassium chromate or sodium chromate and in fused borax or cryohte, and reacts with carbon dioxide, hydrogen, ak, and steam. Sihcon carbide, resistant to chlorine below 700°C, reacts to form carbon and sihcon tetrachloride at high temperature. SiC dissociates in molten kon and the sihcon reacts with oxides present in the melt, a reaction of use in the metallurgy of kon and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new sihcon nitride-bonded type exhibits improved resistance to cryohte. 

Modification of the burning rates, pressure exponents, and temp coefficients of burning rate of the fluorocarbon composites has been accomplished with copper, lead, tin, sodium, ammonium and potassium fluoborates sodium, potassium, lithium, lead, copper and calcium fluorides potassium and ammonium dichromate lead and zinc stearate cesium carbonate potassium and ammonium sulfate copper chromite oxides of magnesium, copper and manganese boron zinc dust and carbon black (Ref 75)... 

Numerous organic syntheses are based on stoichiometric oxidations of hydrocarbons with sodium dichromate and potassium permanganate, or on hydrogenations with alkali metals, borohydrides or metallic zinc. In addition, there are reactions... 

The reaction of zinc oxide, hydrochloric acid, sodium dichromate, and potassium chloride produced zinc yellow as a precipitate, which is a complex compound of zinc, potassium, and chromium. The complex compound is further subjected to filtration, washing, drying, milling, and packaging for use. 

In a review of the course and mechanism of the catalytic decomposition of ammonium perchlorate, the considerable effects of metal oxides in reducing the explosion temperature of the salt are described [1], Solymosi s previous work had shown reductions from 440° to about 270° by dichromium trioxide, to 260° by 10 mol% of cadmium oxide and to 200°C by 0.2% of zinc oxide. The effect of various concentrations of copper chromite , copper oxide, iron oxide and potassium permanganate on the catalysed combustion of the propellant salt was studied [2], Similar studies on the effects of compounds of 11 metals and potassium dichromate in particular, have been reported [3], Presence of calcium carbonate or calcium oxide has a stabilising effect on the salt, either alone or in admixture with polystyrene [4],... 

This is prepared by passing dry hydrogen chloride over chromium, or hydrogen over anhydrous chromium(III) chloride. It is a white solid. If pure chromium is dissolved in dilute hydrochloric acid in the absence of air, a blue solution of the hydrated chloride, containing the hexaaquo-ion [Cr(H20)6]2+. is obtained. The same solution is also obtained by reduction of the + 6 oxidation state (through the + 3) using a solution of a dichromate(VI) and reducing with zinc and hydrochloric acid ... 

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