Double-layer structure and mechanism of electrode reactions: Part II. Nitrobenzene reduction on mercury from aqueous solutions

Kinetic measurements of nitrobenzene (RNO₂) electroreduction to phenylhydroxylamine in aqueous solutions of pH ranging from 2 to 12 were carried out with the polarographic technique under different experimental conditions. In particular, different concentrations of non-specifically and specifically adsorbed supporting electrolytes were employed to change the potential φ_d at the outer Helmholtz plane and/or the charge density q_i at the inner Helm-holtz plane. The effects of these changes are amenable to a straightforward interpretation provided the overall electrode process is assumed to be controlled by the electron-transfer step $RN{O}_{2}H\stackrel{+e}{\to }RN{O}_2{H}^{?}$ (step a) for 2<pH<5, by the heterogeneous protonation step $RN{O}_2^{?}\stackrel{+H^{+}}{\to }RN{O}_{2}H$ (step b) for 6<pH<9, by the electron-transfer step $RN{O}_2^{?}\stackrel{+e}{\to }RN{O}_2^{2?}$ (step c) for pH>11, and by both the parallel steps (b) and (c) for 9<pH<11.     

Calix[4]arene-based Mannich and Schiff bases as versatile receptors for dichromate anion extraction: synthesis and comparative studies

A series of novel calix[4]arene-based Mannich (5 and 6) and Schiff base (9–11) receptors have been synthesized and characterized by various analytical techniques. Competitive two-phase extraction experiments of these novel calix[4]arene amine- and imine-containing derivatives revealed a strong affinity for dichromate anions $\left({\text{Cr}}_2{\text{O}}_7^{2?}/{\text{HCr}}_2{\text{O}}_7^{?}\right)$. The protonated alkylinium form of 5, 6 and 9–11 proved to be effective extractants for transferring the dichromate anions from an aqueous into an organic phase. Moreover, the extraction of dichromate anions by 5 and 9 in the presence of competitive anions such as F^?, Cl^?, Br^?, ${\text{NO}}_3^{?}$, ${\text{NO}}_2^{?}$, ${\text{PO}}_4^{3?}$ and ${\text{SO}}_4^{2?}$ showed that 5 and 9 could be selective anion receptors for dichromate anions in the presence of those anions.     

Dioxygen affinities and catalytic oxidation performance of cobalt（Ⅱ） hydroxamates with benzo-15-crown-5 pendants

The oxygenation constants(Ko_2)of cobalt(Ⅱ)hydroxamates(CoL_2~1-CoL_2~3)with benzo-15-crown-5(B15C5)pendants were measured over the range of-5 to 20℃,and the values of thermodynamic parameters(ΔH~0 andΔS~0)were calculated based on these(No_2)values.Meanwhile,these crowned complexes were employed to the oxidation for p-xylene to p-toluic acid with air at 110Δunder normal atmospheric pressure.The effects of B15C5 pendant and the length of chain bonded to B15C5 in these complexes on the O_2-binding capabilities and oxidation for p-xylene were investigated with the comparison of crown-free analogues CoL_2~4.     

Electrochemical reduction of benzenesulphenyl chloride in aprotic solvents

The cathodic behaviour of benzenesulphenyl chloride has been studied at a platinum electrode in acetonitrile by using cyclic voltammetry and controlled potential electrolysis. It has been evidentiated that PhSCl gives rise, in an one-electron reduction process, to PhSSPh and Cl^? according to $2PhSCl+2{\mathit{e}}^{?}\to PhSSPh+2{Cl}^{?}$ The chloride ions so generated catalyze the subsequent hydrolysis of PhSCl caused by traces of water present in the organic solvent, i.e. $2PhSCl+H_{2}O\stackrel{{Cl}^{?}}{\to }PhSOSPh+2HCl$ which is concomitant with the electrodic reaction and hence accounts for the overall n_e value lower than one. The same results have been obtained in nitromethane while in dimethyl-formamide the above reported hydrolysis reaction seems to be catalyzed by the solvent itself.