Mond reaction

This is the Mond reaction, first developed by Ludwig Mond in 1890. It is still used forthe production and purification of metallic nickel. A similar reaction is used for the production of Fe(CO)5 but higher temperature is required. 

Easily decomposed, volatile metal carbonyls have been used in metal deposition reactions where heating forms the metal and carbon monoxide. Other products such as metal carbides and carbon may also form, depending on the conditions. The commercially important Mond process depends on the thermal decomposition of Ni(CO)4 to form high purity nickel. In a typical vapor deposition process, a purified inert carrier gas is passed over a metal carbonyl containing the metal to be deposited. The carbonyl is volatilized, with or without heat, and carried over a heated substrate. The carbonyl is decomposed and the metal deposited on the substrate. A number of papers have appeared concerning vapor deposition techniques and uses (170—179). 

About 70% of the western world s supply of nickel comes from iron and nickel sulfide ores that were brought close to the surface nearly 2 billion years ago by the violent impact of a huge meteor at Sudbury, Ontario. The ore is first roasted (heated in air) to form nickel(II) oxide, which is reduced to the metal either elec-trolytically or by reaction with hydrogen gas in the first step of the Mond process ... 

CVD developed slowly in the next fifty years and was limited mostly to extraction and pyrometallurgy for the production of high-purity refractory metals such as tantalum, titanium, and zirconium. Several classical CVD reactionswere developedatthattimeincludingthecarbonyl cycle (the Mond process), the iodide decomposition (the de Boer-Van Arkelprocess)andthemagnesium-reduction reaction (the Kroll process). 

According to the free energy change associated with the pertinent reaction, nickel will form nickel tetracarbonyl at low temperatures, and this carbonyl will become unstable and revert back to nickel and carbon monoxide at moderate temperatures. The Mond process for refining nickel is based on these features. In this process, impure nickel is exposed to carbon monoxide gas at 50 °C, whereby volatile nickel tetracarbonyl (Ni(CO)4) forms. No impurity present in the crude nickel reacts with carbon monoxide. Since formation of the... 

The Mond process separates nickel from other metals by passing CO over the hot metal mixture. The nickel reacts to form a volatile compound (called nickel carbonyl), which is then swept away by the gas stream. The reaction is... 

The Mond process for purifying nickel involves the reaction of impure nickel with carbon monoxide at about 150°C to give nickel tetracarbonyl. The nickel tetracar-bonyl then decomposes to pure nickel at about 230°C ... 

In the Mond process for purifying nickel, the volatile nickel carbonyl, Ni(CO)4, is produced by the reaction ... 

As variations of Rh-catalyzed cycloisomerization Widenhoefer and coworkers have developed asymmetric 1,6-enyne cyclization/hydrosilylation reactions by using the Rh(I)/biphemp system excellent de and ee were obtained [42]. Brum-mond et al. also discovered a rhodium(I)-catalyzed allenic Alder-ene reaction that... 

The vapor pressure of dicobalt octacarbonyl is quite low at room temperature the reported (Mond, Hirtz, and Cowap, 26) value is 0.072 mm. at 15°. There are very little other published data concerning the vapor pressure probably because of the difficulty in securing accurate data. The equilibrium dissociation constant for the reaction... 

With the advent of the chromium trioxide-3,5-dimethylpyrazole complex as an oxidant - allylic oxidation has become far more valuable as a synthetic transfonnation. The reagent was applied by Sala-mond to the allylic oxidation of cholesteryl benzoate to give the correspondbg A -7-ketone (equation 35). However, a 20 molar excess of reagent was still requii to effect the reaction in less than 30 min at room temperature. 

Together with Ni(CO)4 andFe(CO)5, dicobaltoctacarbonyl, Co2(CO)g (1), was among the earliest metal carbonyls (see Metal Carbonyls) to be detected and characterized by Mond and coworkers." It was prepared from frnely divided metal (or by hydrogen reduction of the oxide, CoO) in a Cu-lined autoclave made from Ni steel at 150 °C and a CO pressure of 30-40 bar. Other preparations employ reductive carbonylation of cobalt salts, mainly Co(OAc)2, or the carbonylation of an alkaline cobalt cyanide solution. The acetate salt is also the common precursor for Co2(CO)g or Co(CO)4H in the Cocatalyzed hydroformylation (see Hydroformylation) process (Section HCo(CO)4 in Hydroformylation Reactions ). 

NH4)2S04+Na2.S04. When the normal sulphate is heated ammonia is given off and the bisulphate reformed (NH4)2S04-fNa2S04=2NH3-f-2NaHS04. The first-named reaction is not complete, and L. Mond considers that there is no reaction... 

Ni(C0)4 is a volatile, extremely toxic liquid that must be handled with great caution. It was first observed in Mond s study of the reaction of CO with nickel valves. Because the reaction can be reversed at high temperature, coupling of the forward and reverse reactions has been used commercially in the Mond process for obtaining purified nickel from ores. Other binary carbonyls can be obtained from direct reaction of metal powders with CO, but elevated temperatures and pressures are necessary. 

Acetoxyjmercori dimethyl ether is prepared in the same way as the ]>receding compound, hut the reaction takes longer to complete. Yield 95 per cent. It forms fine white needles, sintering at C. and melting at 86 C. The (Monde yields white needles, M.pt. 92 C., and when iieated with inetlni iodide at lOO" . practically 1 mol. of ethylene is produced and mereuric iodide formed. 

By the latter part of the nineteenth century, the Solvay process for the production of sodium bicarbonate had become very important commercially. Ammonium chloride formed as a by-product in this reaction, and chemists sought ways to convert it to chlorine on a commercially feasible scale. The reaction vessels contained valves made of nickel, which corroded severely during many of these reactions. Mond carried out a detailed study on this corrosion, and found that carbon monoxide was the active agent (180) ... 

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