Chromium formate decomposition

Baker RTK, Harris PS, Thomas RB, Waite RJ. Formation of filamentous carbon from iron, cobalt and chromium catalyzed decomposition of acetylene. J Catal 1973 30 86-95. 

The important (3-stabilizing alloying elements are the bcc elements vanadium, molybdenum, tantalum, and niobium of the P-isomorphous type and manganese, iron, chromium, cobalt, nickel, copper, and siUcon of the P-eutectoid type. The P eutectoid elements, arranged in order of increasing tendency to form compounds, are shown in Table 7. The elements copper, siUcon, nickel, and cobalt are termed active eutectoid formers because of a rapid decomposition of P to a and a compound. The other elements in Table 7 are sluggish in their eutectoid reactions and thus it is possible to avoid compound formation by careful control of heat treatment and composition. The relative P-stabilizing effects of these elements can be expressed in the form of a molybdenum equivalency. Mo (29) ... 

Electrobalances suitable for thermogravimetry are readily adapted for measurements of magnetic susceptibility [333—336] by the Faraday method, with or without variable temperature [337] and data processing facilities [338]. This approach has been particularly valuable in determinations of the changes in oxidation states which occur during the decompositions of iron, cobalt and chromium oxides and hydroxides [339] and during the formation of ferrites [340]. The method requires higher concentrations of ions than those needed in Mossbauer spectroscopy, but the apparatus, techniques and interpretation of observations are often simpler. 

Stirring chromium trioxide (added in small portions) with the unheated solvent leads to the formation of a complex useful for oxidising alcohols to carbonyl derivatives. The trioxide must not be crushed before being added to the solvent, because violent decomposition may then occur. 

The reaction of olefin epoxidation by peracids was discovered by Prilezhaev [235]. The first observation concerning catalytic olefin epoxidation was made in 1950 by Hawkins [236]. He discovered oxide formation from cyclohexene and 1-octane during the decomposition of cumyl hydroperoxide in the medium of these hydrocarbons in the presence of vanadium pentaoxide. From 1963 to 1965, the Halcon Co. developed and patented the process of preparation of propylene oxide and styrene from propylene and ethylbenzene in which the key stage is the catalytic epoxidation of propylene by ethylbenzene hydroperoxide [237,238]. In 1965, Indictor and Brill [239] published studies on the epoxidation of several olefins by 1,1-dimethylethyl hydroperoxide catalyzed by acetylacetonates of several metals. They observed the high yield of oxide (close to 100% with respect to hydroperoxide) for catalysis by molybdenum, vanadium, and chromium acetylacetonates. The low yield of oxide (15-28%) was observed in the case of catalysis by manganese, cobalt, iron, and copper acetylacetonates. The further studies showed that molybdenum, vanadium, and... 

Since the rate of formation of cementite is determined by nucleation, and therefore proceeds more rapidly in fine-grained steels, it follows that the T-T-T diagram will show a more rapid onset of austenite decomposition than in steels of the same composition, but a coarser grain size. The shape of the T-T-T curve is also a function of the steel composition, and is altered by the presence of alloying elements at a low concentration. This is because the common alloying elements such as manganese, nickel and chromium decrease... 

Triethanolamine complexes of chromium(iii) have been reported and characterized in i.r. spectra and thermal-decomposition studies. The chromium(iii) nitrilotriacetato-complex [CrL(H20)2] [L = N(CH2C02)3 ] complexes with thallium(iii) to give [ CrL3(0H)(H20) gTl] with a formation constant of 9 3 X 10 at 25 The hydrolysis and dimerization of [CrLlOHljV ... 

Chromium complexes in general are poor catalysts for the epoxidation of alkenes with TBHP due to the decomposition of the oxygen donor with formation of molecnlar oxygen . Epoxidation reactions with this metal are known with other oxygen transfer agents than peroxides (e.g. iodosylbenzene) and will not be discnssed here. 

WarningI Tris(acetonitrile)chromium tricarbonyl is highly pyrophoric and degrades rapidly when exposed to oxygen, but is reasonably stable in THF solution. Best yields are obtained when this intermediate is as free of acetonitrile as possible while avoiding formation of the green colored [Cr(lll)] decomposition product, which develops on contact with air. 

The formation and decomposition of Crv in aqueous and non-aqueous media during the oxidation of organic substrates such as oxalic acid and ethylene glycol by potassium dichromate has been recognized for some time. No study resulted in the isolation of a stable, well-characterized chromium(V) complex until 1978 when potassium bis(2-hydroxy-2-methylbutyrato)oxochromate(V) monohydrate was prepared from chromium trioxide and the tertiary a-hydroxy acid in dilute perchloric acid according to equation (91). The Crv, which is... 

We believe that catalysis occurs by formation of a complex between acetaldehyde, peracetic acid, and the metal ion in the 3+ oxidation state. The metal ion could be acting as a superacid as for peracetic acid decomposition, although oxidation-reduction reactions within the complex cannot be ruled out. Here again, we have found a disturbing lack of catalytic activity of other trivalent metals (aluminum, iron, and chromium). Simple acid catalysis is not as effective as proved when using p-toluenesulfonic acid and acetyl borate. This indicates that at least more than one coordination position is needed to obtain a complex of the proper configuration. 

Chromium tetraphenyl hydrogen carbonate, (C6H5)4Cr.HC03. 2HaO.—An aqueous solution of the tetraphenyl base is saturated with carbon dioxide and concentrated over sulphuric acid in vacuo. The residue is treated with alcohol and the product precipitated by ether. Orange crystals separate, M.pt. 110° to 1110 C., prolonged desiccation over phosphorus pentoxide causing decomposition and formation of diphenyl. 

It is now generally admitted that this reaction involves both one-electron and two-electron transfer reactions. Carbonyl compounds are directly produced from the two-electron oxidation of alcohols by both Crvl- and Crv-oxo species, respectively transformed into CrIV and Crm species. Chromium(IV) species generate radicals by one-electron oxidation of alcohols and are responsible for the formation of cleavage by-products, e.g. benzyl alcohol and benzaldehyde from the oxidation of 1,2-diphenyl ethanol.294,295 The key step for carbonyl compound formation is the decomposition of the chromate ester resulting from the reaction of the alcohol with the Crvl-oxo reagent (equation 97).296... 

The Ji-complexes formed between chromium(O), vanadium(O) or other transition metals, and mono- or poly-fluorobenzene show extreme sensitivity to heat and are explosive [1,2], Hexafluorobenzenenickel(O) exploded at 70°C [3], and presence of two or more fluorine substituents leads to unstable, very explosive chromium(O) complexes [1]. Apparently, the aryl fluorine atoms are quite labile, and on decomposition M—F bonds are formed very exothermically. Laboratory workers should be wary of such behaviour in any haloarenemetal Ji-complex of this type [1]. However, in later work, no indications of explosivity, or indeed of any complex formation, were seen [4]. Individually indexed compounds are ... 

The shorter-term exposure experiments show that some portion of the organically-bound chlorine, such as trichlorethane or its decomposition products, remains absorbed on a 304 stainless steel surface, even after heating at 35-40°C in a high vacuum. Conversion to an ionic species begins after a short contact period and can be detected using XPS. Formation of the ionic chloride is likely the result of hydrolysis by water also absorbed on the surface, and is perhaps catalyzed by the surface metal oxides. Further atmospheric exposure up to a few months increases the relative amount of the ionic form of chlorine. The composition of the surface oxide layer was altered, with chromium oxide replacing iron oxide as the major species. There was further evidence that chlorine was present as iron chloride, perhaps up to 5% of the surface film. The conditions under which oxidation of such surfaces occurred are quite comparable to those which could occur on steel surfaces in industrial usage. 

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