Alkylsilanes anodic oxidation

Similarly to the low chemical reactivity of (simple) alkylsilanes devoid of functional groups, the electrochemical reactivity of simple alkylsilanes is quite low. Klingler and Kochi measured the oxidation potentials of tetraalkyl derivatives of group-14-metal compounds by using cyclic voltammetry3. These compounds exhibit an irreversible anodic peak in acetonitrile. The oxidation potential (7 p) decreases in the order of Si>Ge>Sn>Pb as illustrated in Table 1. This order is the same as that of the gas-phase ionization potentials (7p). The absence of steric effects on the correlation of Ev with 7p indicates that the electron transfer should take place by an outer-sphere mechanism. Since tetraalkylsilane has an extremely high oxidation potential (>2.5 V), it is generally difficult to oxidize such alkylsilanes anodically. 

Benzylsilanes and allylsilanes are easily oxidized anodically compared with alkylsilanes and arylsilanes. Benzylsilanes exhibit irreversible cyclic voltammetric waves. It is notable that their oxidation potentials (Ep) are markedly less positive than those of the unsilylated parent compounds owing to the a-jr interaction (Table 3)10a. It is interesting that a-trimethylsilylation of xylenes markedly decreases their oxidation potential while additional a -trimethylsilylation makes a little change (Table 3). It has also been reported that a a, a-interacting system (the neighboring C—Si bonds) in addition to a a-ir interaction caused a significant decrease of the oxidation potentials1013. 

An equivalent circuit can be derived for the surface-bound membrane formed in this work similar in a manner to the approach taken for porous anodic films and porous electrodes (41-46). An equivalent circuit network, proposed in Figure 8a, corresponds to the model in Figure 7. This network has three RC subnetworks that represent the oxide layer, the surface-bound membrane layer, and the double layer. Cox and Rox are the capacitance and resistance of oxide. and Rdl are the double-layer capacitance and the polarization resistance, known as the charge transfer resistance at the membrane-water interface. For the subnetwork of the surface-bound membrane layer, one branch represents a tightly packed alkylsilane and lipid bilayer in series, and the other branch represents the pores and defects through the bilayer. Calk, Clip and Ralk, Rhp are the capacitances and resistances of... 

Many applications of cationic clays are directed toward the detection of heavy metals [1]. hi this case, the analytical method followed is very similar to an anodic stripping voltammetric technique a step reducing pre-concentrated metal ions to the zero valence state is performed and the analytical signal is collected in the subsequent anodic re-oxidation step [61]. The selectivity of the clay toward a target metal ion can be improved by a functionalization of the material with suitable alkylsilane derivatives [64, 65, 80] or by intercalation of a specific organic ligand inside the clay interlayers [66, 67, 81]. 

---