Goldschmidt reaction

Goldschmidt reaction The use of A1 powder for the reduction of metal oxides. 

In the Goldschmidt reaction, mentioned in Chapter VI, a metal oxide is reduced by aluminum powder to the free metal. The reaction is useful for obtaining transition metals, such as vanadium, chromium, and manganese, which are too reactive to be produced by reduction of their oxides with hydrogen. The reaction... 

What nonmetals are advantageously prepared by the Goldschmidt reaction ... 

The latter two reactions are frequently used for detecting the presence of a hydroxyl group (Goldschmidt). 

Electrolysis of salts of fatty acids gives free radicals which are capable of reacting with added substrates. For instance, when water-free potassium acetate is electrolyzed in the presence of polymerizing substances (e.g., styrene) methyl groups are incorporated as end groups into the polymer. Goldschmidt et ai. analyzed the products formed in the electrolysis of potassium propionate in propionic acid and showed that they could be accounted for by the following reaction sequence ... 

Goldschmidt and Beer have examined the products formed during the thermal decomposition of diacyl peroxides of the type [COgMe —(CHziw—CHz—COO] 2, where n = 1 and 3, in the presence of a series of organic compounds including pyridine and acridine. The products and yields of the reaction with some aromatic and heterocyclic compounds are shown in Table VI. As expected, acridine and... 

Goldschmidt s mechanism was widely used by Hinshelwood240,2411 and Smith242 2431 for dilute solutions this corresponds to the experimental conditions for which relation (48) has been established. More recently, Van der Zeeuw244 applied Goldschmidt mechanism to the reaction of phthalic anhydride with model alcohols in concentrated solutions. 

A detailed mechanism of Goldschmidt s process has not been given two reaction paths are possible either proton transfer to the acid with the formation of RC(OH) (in which case the slow step would be an Aac2 Ingold mechanism) or nucleophilic attack of the carbonyl group of the acid on the protonated alcohol. The second mechanism would require an alkyl scission (A l). In more recent studies2501, it has been shown that scission in most cases is of the acyl type and particularly in the examples studied by Goldschmidt. 

When no protonic catalyst is added it is the carboxylic acid which acts as a catalyst in 1896, Goldschmidt already showed that in this case the reaction order with respect to acid is greater than unity and Hinshelwood2511 suggested the following relation for the esterification rate ... 

This is a weathering reaction. Sillen argued that Goldschmidt s reaction could also go the other direction. The reverse reaction would be called reverse weathering. 

Thermit Also spelled Thermite, and also called the Goldschmidt process. The reaction of metallic aluminum with a metal oxide is very exothermic and can be used to liberate other metals from their oxides, or simply as a source of heat. In the latter case, iron oxide is used ... 

This reaction and its applications were discovered developed by Hans Goldschmidt... 

The basic reaction underlying the combustion of many gasless delay formulations is the Goldschmidt or thermite reaction where a metal powder and a metallic oxide interact in an oxidation-reduction reaction manner with the evolution of a large amount of heat but very little or no gas. Consequently, these formulations are used where no vent or very little vent is provided in the ammunition. Gasless delay formulations tend to burn faster under higher consolidation as the points of contact of fuel and oxidizer increase. This is because the reaction in this case is a solid state reaction by diffusion. 

Modifications of the Goldschmidt thermite process may also be employed for the preparation of the iron-vanadium alloy. The crushed vanadates or vanadium pentoxide are mixed with the necessary amount of iron scalings or turnings and fluxes, and introduced into a gas-fired open-hearth furnace or into an iron crucible provided with a refractory lining and previously heated to redness. The reactions taking place are ... 

One method of preparation consists in a modification of the Goldschmidt process. Niobium pentoxide is mixed with an alloy of the rare earths, called mixed metal, obtained in the manufacture of thorium nitrate, and consisting roughly of 45 per cent, of cerium, 20 per cent, of lanthanum, 15 per cent, of didymium, and about 20 per cent, of other rare-earth metals. The reaction is carried out in a magnesia-lined crucible, and is started with a firing mixture of barium peroxide, potassium chlorate, and aluminium powder. Considerable evolution of heat takes place and the reduction is extremely rapid a button of niobium is obtained 4 which, however, is not pure. 

Campbell et al.[97] found that the yield of the Goldschmidt-Wick-type reaction was lower with C2-substituted monoalkyl malonates than with unsubstituted monoalkyl malonates. They therefore suggest selective C2 alkylation of a malonyl residue already incorporated into a PMRI-dipeptide (Scheme 8)J73] Unfortunately, no experimental details are available for what might potentially be an important synthetic manipulation. 

GOLDSCHMIDT REDUCTION PROCESS. Reaction of oxide), of various metals with aluminum lo yield aluminum oxide and the free metal. This inaction has been used to produce certain metals, e g. chromium and zirconium, from oxide ores and it is also used in welding (iron oxide plus aluminum giving metallic iron and aluminum oxide, plus considerable heat). (Thermite process. ... 

THERMITE. A mixture of ferric oxide and powdered aluminum, usually enclosed in a metal cylinder and used as an incendiary bomb, invented by the German chemist Hans Goldschmidt around 1900. On ignition by a ribbon of magnesium, the reaction produces a temperature of 2200°C, which is sufficient to soften steel. This is typical of some oxide/metal reactions that provide their own oxygen supply and thus are very difficult to stop. 

---