Tin, reduction

With the exception of antimony (V), which requires the presence of iodide for its reduction, all species can be reduced in an acid medium at a pH of 1 -2. However, the reduction of some species, including antimony (III), arsenic (III), and all tin species, will also proceed at higher pH, where arsenic (V) and antimony (V) are not converted to their hydrides. This effect permits the selective determination of the various oxidation states of these elements [714, 716]. In the case of tin, reduction can be achieved at the pH of the Tris-HCl... 

Taking i nto c onsideration t hese d ata o n z inc d istribution we c an p ropose t he mechanism with zinc codeposition in the process of the tin reduction. It can be confirmed by the calculation of redox tin and zinc potentials with obstacles in mass transfer and real ion concentrations in the solution and near the growing surface. 

Like Walker, Snyder and colleagues found that catalytic hydrogen conditions with paUadium-on-carbon improves the yield of indoles and are superior to the tin reduction of Stephen (Scheme 3) [5]. Snyder suggests that the mechanism of this indole synthesis involves initial reduction of the o-nitrobenzylcyanide to the imine 1 followed by cycli-zation and loss of ammonia and tautomerization of indolenine 2 to indole (equation 3), rather than Walker s mechanism via 2-aminoindole. 

The data in Figure 9.27 show an obvious correlation between the structure of the double layer and kinetics of Sn(II) reduction both ig and C j vary in the same manner. The decrease in C j with time seems to arise from the progressive saturation of the interface with an adsorbed TEG, causing an increasing inhibition of tin reduction. This manifests itself in the respective lowering of the exchange current density. A more than 10-fold decrease in ig is observed after 2 h, as compared with the surfactant-free solution. 

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