Silver cerium reactions

The manganese-benzidine reaction, as just described, cannot be used in the presence of other oxidizing agents or autoxidizable substances which likewise oxidize benzidine (chromates, ferricyanides, cobalt, thalliumi, silver, cerium i salts). In such cases, special procedures must be used. 

Mitsudome T, Mikami Y, Matoba M, Mizugaki T, Jitsukawa K, Kaneda K (2012) Design of a silver-cerium dioxide core-shell nanocomposite catalyst for chemoselective reduction reactions. Angew Chem Int Ed 51 136-139... 

Solvent for Electrolytic Reactions. Dimethyl sulfoxide has been widely used as a solvent for polarographic studies and a more negative cathode potential can be used in it than in water. In DMSO, cations can be successfully reduced to metals that react with water. Thus, the following metals have been electrodeposited from their salts in DMSO cerium, actinides, iron, nickel, cobalt, and manganese as amorphous deposits zinc, cadmium, tin, and bismuth as crystalline deposits and chromium, silver, lead, copper, and titanium (96—103). Generally, no metal less noble than zinc can be deposited from DMSO. 

Copper(II) and cerium(IV) have been studied as oxidants in acetonitrile. The copper(II)-copper(I) couple has an estimated electrode potential of 0.68 V relative to the silver reference electrode. It has been studied as an oxidant for substances such as iodide, hydroquinone, thiourea, potassium ethyl xanthate, diphenylbenzidine, and ferrocene. Cerium(IV) reactions are catalyzed by acetate ion. Copper(I) is a suitable reductant for chromium(VI), vanadium(V), cerium(IV), and manganese(VII) in the presence of iron(III). For details on many studies of redox reactions in nonaqueous solvents, the reader is referred to the summary by Kratochvil. ... 

However, in regard to the reactions of tungsten with metallic elements, the situation is quite different. A large number of metals exist which fail to react with tungsten, like the alkali metals, the alkaline earth metals with the exception of beryllium, the rare earth metals with the exception of cerium, and especially the elements scandium, yttrium, lanfiianiun, copper, silver, gold, zinc, cadmium, mercury, indium, thallium, tin, lead, antimony, bismuth, and polonium. 

Compared to iron(III), copper(ll), and especially manganese(III) and cerium(IV) other metals have found less application for the oxidative generation of radicals [1]. An exception is cobalt(III)-mediated radical reactions, based on the pioneering work of Iqbal et ah, which was recently reviewed [20] (see also Volume 1, Chapter 1.8). Some examples of oxidative couplings of silyl enol ethers 44 in the presence of silver(I) oxide were developed [21]. However, there is no advantage over copper(II)-mediated radical reactions, since the reagent is more expensive and the 1,4-diketones 45 are isolated in only moderate yield (Scheme 15). 

The first step in the GC determination of carbon and hydrogen is quantitative oxidation of the sample organic compounds, usually with a catalyst. Copper oxide is commonly used, but the reaction is relatively slow and elevated temperatures of about 900°C are required. With silver permanganate the reaction temperature is reduced to 550°C [34, 35] and with cobalt oxide to 750°C [36, 37] both compounds provide a shorter oxidation time. Other catalytic oxidizing agents, such as nickel oxide [38, 39] and cerium(IV) oxide [40], have been found promising. Platinum can also be used, especially when it is necessary to avoid the retention of any oxidation products by the solid catalyst. 

In coulometric titrations, a constant current generates the litrant eleclrolytically. In some analyses, Ihe active electrode process involves only generation of the reagent." An example is the titration of halides by silver ions produced at a silver anode. In other titrations, the analyte may also be directly involved at the generator electrode. An example of this type of titration is the coulometric oxidation of iron(ll)-in part by elec-trolytic.illy generated cerium(l V) and in part by direct electrode reaction (Section 24B-2). Under any circumstance. the net process must approach 100% current efficiency with respect to a single chemical change in the analyte. 

A -iodosuccinimide (lequiv.) and p-toluenesulfonic acid (10mol%) for Ih, to form an a-iodoketone 153 in situ. In the second reaction step, to this milling vessel were added primary amine (2equiv.), 3-dicarbonyl compound 155 (1.5equiv.), cerium(IV) ammonium nitrate (5%), and silver nitrate (1 equiv.) and ball milled for another 1 h. The scope of this pyrrole synthesis was broader than the one described in the literature for previous variations of the Hantzsch reaction, since nitrogen-unsubstituted pyrroles and also double Hantzsch-like reactions based on the use of diamines as starting materials were successfully carried out. 

Several studies have been carried out in sulphate media. The mechanism of oxidation of 1-naphthylamine and 8-aminonaphthalene-l-sulphonic acid has been described and complex formation invoked in the reactions with benzilic acid and formaldehyde. Hydrochloric acid reduces cerium(iv) at a measurable rate at room temperature and silver(i) acts as a catalyst for the reaction. The activated complex is considered to involve both sulphatocerate and chloride anions. The large overall heats of reaction with a-thiolocarboxylic acids and thioureas have been... 

Detection is carried out with cerium (IV) stdphate (Bgt. No. 37). It cannot be used with layers impregnated with silver nitrate, nor with alumina layers. Iodine vapour or solution (Rgt. No. 143) or para-formaldehyde-phosphoric acid (Rgt. No. 194) can be used also and 2,4-dinitrophenylhydrazine (Rgt. No. 82) with alkaloids containing a keto group. The cerium (IV) sulphate reagent is recommended as a universal detection agent zl -unsaturated compounds yield a colour reaction even in the cold. Iodine vapour permits non-destructive detection of the sterol alkaloids, so that they may be subsequently isolated unchanged. 

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