Silver ions, reactions

There are indications that another type of catalysis is present in the reaction between hydroquinone and silver ions in alkaline solution. The increase of rate with increasing hydroquinone concentration is greater than direct proportionality. This situation is similar to that observed in the oxygen oxidation of durohydroquinone (tetramethylhydroquinone) (James and Weissberger, 16) where the quinone formed in the reaction catalyzes subsequent oxidation. A direct check on quinone catalysis of the hydroquinone-silver ion reaction was not made, since quinone is unstable in alkaline solution, particularly in the presence of sulfite which reacts with it. Experiments were made, however, on the reaction between durohydroquinone and silver ion. This reaction shows the same dependence of rate upon the square root of the silver ion concentration as the hydroquinone reaction does. Addition of duroquinone to the reaction mixture produces a definite acceleration, as shown in Table II. 

Thus, an equation in agreement with the experimental data for the hydroquinone-silver ion reaction can be derived either on the basis of the assumption that adsorption of silver ions by the silver is a prelude to the reaction, or on the basis of the assumption that the rate-controlling step in an electrode process is the rate of transfer of electrons to the silver electrode. The first mechanism carries with it the assumption that a silver ion adsorbed by silver is more easily reduced than an ion in solu-... 

The same considerations can be applied to the mechanism of the hydroxylamine-silver ion reaction as have been given already for the hydroquinone-silver ion reaction. Bagdasar yan s equation adequately expresses the dependence of rate on the silver ion concentration and on the surface of the catalyst, but not the dependence on the hydroxylamine concentration. The latter dependence, on the other hand, would be in agreement with the assumption that hydroxylamine is adsorbed by the silver prior to reaction. 

The data for the p-phenylenediamine-silver ion reaction are not accounted for by Bagdasar yan s treatment. On the basis of an adsorption mechanism, the data would suggest that the important phase for the catalyzed reaction is adsorption of the p-phenylenediamine by the silver catalyst. The extent of the adsorption would depend upon the surface conditions of the catalyst, which apparently depend on changes in the protective colloid or in the salt concentration. A catalytic mechanism involving activation of the p-phenylenediamine by the catalyst would be consistent with the observation of Weissberger and Thomas that colloidal silver markedly catalyzes the oxygen oxidation of p-phenylenediamine. 

Transition metal complexes containing catecholate and semiquinone ligands have been reviewed by Pierpont and Buchanan.336 The syntheses of catecholate adducts of platinum group metals by oxidative addition of benzoquinone (BQ) have been reported (reaction 92).337 The coordinated catechol can then be oxidized to the semiquinone with silver ion (reaction 93). In reactions (92) and (93), L M = lr(Cl)(CO)(PPh3)2] and the benzoquinones (BQ) are shown in (146). The oxidative addition of phenanthrenequinone to [Ir(Cl)(CO)(PPh3)2] has also been cited.338... 

Benzocyclopropene (88) and naphtho[h]cyclopropene react with various alkenic substrates to give cy-cloaddidon piquets in the presence of silver ion. Reaction of (88 equation 39) with butadiene assisted by 1 mol % of AgBp4 in benzene (0 C, 30 min) gives (89) and (90). Dimethylallene (91 equation 40) and oct-4-yne (95 equation 41) also react readily with (88) in the presence of silver ion to give the corresponding cycloaddition products (92), (93) and (96), together with acyclic products (94) and (97). 

Fig. 4. Sulfide-persulfate-silver ion reaction a) batch Pt-potenial evolution. Initial concentrations = 4.2.10 M ISaOl"" = 0.1 M ...

Fig. 5. Oxalic acid-persulfate-silver ion reaction, a) Batch Pt-evolution trace. Initial concentrations (C00H)2 - = 1.10 M, S208 = 0.1 M, lAg li = 4.5 10 M, iHaSO I- = 0.05 M, T = 25°C.

The alkali metal tetrahydridoborates are salts those of sodium and potassium are stable in aqueous solution, but yield hydrogen in the presence of a catalyst. They are excellent reducing agents, reducing for example ion(III) to iron(II). and silver ions to the metal their reducing power is used in organic chemistry, for example to reduce aldehydes to alcohols. They can undergo metathetic reactions to produce other borohydrides, for example... 

Silver Thiocyanate. Silver thiocyanate, AgSCN, is formed by the reaction of stoichiometric amounts of silver ion and a soluble thiocyanate. 

The darkening reaction involves the formation of silver metal within the silver haUde particles containing traces of cuprous haUde. With the formation of metallic silver, cuprous ions are oxidized to cupric ions (1,4). The thermal or photochemical (optical bleaching) reversion to the colorless or bleached state corresponds to the reoxidation of silver to silver ion and the reduction of cupric ion to reform cuprous ion. 

Fig. 9. Corrosion model of silver development. As the haUde ion, X, is removed into solution at the etch pit, the silver ion,, travels interstitiaHy, Ag/ to the site of the latent image where it is converted to silver metal by reaction with the color developer, Dev. Dev represents oxidized developer.

The dye is initially linked to a ballasted thiazoUdine, which reacts with silver to form a silver iminium complex. The alkaline hydrolysis of that complex yields an alkali-mobile dye. Concomitantiy the silver ion is immobilized by reaction with the ballasted aminoethane thiol formed by cleavage of the thiazolidine ring. 

Since a few protective groups cannot satisfy all these criteria for elaborate substrates, a large number of mutually complementary protective groups are needed and, indeed, are becoming available. In early syntheses the chemist chose a standard derivative known to be stable to the subsequent reactions. In a synthesis of callistephin chloride the phenolic —OH group in 1 was selectively protected as an acetate. In the presence of silver ion the aliphatic hydroxyl group in 2 displaced... 

The perfluoroalkylsilver complexes exist in a dynamic equilibrium in solution with solvated silver ion and anionic perfluoroalkylsilver complexes such as Ag[CF(CF5) r [277] The triflnoromethylated silver complex, Ag(CF3)4 , is prepared via reaction of bis(trifIuoromethyl)cadmium with silver nitrate in acetoni trile [278]... 

For simplicity a cell consisting of two identical electrodes of silver immersed in silver nitrate solution will be considered first (Fig. 1.20a), i.e. Agi/AgNOj/Ag,. On open circuit each electrode will be at equilibrium, and the rate of transfer of silver ions from the metal lattice to the solution and from the solution to the metal lattice will be equal, i.e. the electrodes will be in a state of dynamic equilibrium. The rate of charge transfer, which may be regarded as either the rate of transfer of silver cations (positive charge) in one direction, or the transfer of electrons (negative charge) in the opposite direction, in an electrochemical reaction is the current I, so that for the equilibrium at electrode I... 

Copper metal can reduce silver ions to metallic silver The copper is oxidized to copper ions according to the reaction... 

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