Polarographic Behaviour of the Hexa-ammine-chromium(III) Ion: Role of Hydrogen Ions
HEXA-AMMINECHROMIUM(III) ion in acetate buffer solutions is reduced at the dropping mercury electrode, and gives two polarographic waves. The first wave, which is well defined, is considered to be a one-electron reduction of Cr(III) to Cr(II)1. Its half-wave potential at 25° C was found to be −0.970 V versus saturated calomel electrode in 0.1 M acetate buffer solution which contained 0.9 M potassium chloride and 0.005 per cent gelatin (Fig. 1, curve a). The limiting current of this wave was diffusion-controlled and proportional to the concentration of the complex ion up to 5 mM. Both the half-wave potential and the diffusion current remained constant when the pH was varied from 4.5 to 5.45. No change was observed when potassium chloride was replaced by ammonium chloride at the constant ionic strength. The plot of log ī/(īd − ī) versus E, where ī means the average current, īd the average diffusion current, and E, the potential of the dropping mercury electrode, gave a straight line with a reciprocal slope of 64 mV, whereas the examinations with Kalousek's circuit and alternating current polarograph showed that this wave has nearly irreversible character.
Electrode processes followed by chemical reactions involving electroactive species: I. The effect of ethylenediaminetetraacetate on the polarographic reduction waves of hexaquochromium(III) and hexamminechromium(III)
Abstract The effect of ethylenediaminetetraacetate (EDTA) on the one-electron reduction process of hexamminechromium(III) and hexaquochromium(III) at the dropping mercury electrode has been investigated in acid media. In the piesence of EDTA, chromium(II) produced by the reduction reacts with EDTA to form a Cr(II)-EDTA complex. As long as the potential is sufficiently positive, this complex is oxidized at the electrode, and a current dependent on the rate at which chromium(II) combines with EDTA is observed.
Benign approaches for the synthesis of bis-imine Schiff bases
Pure bis-imine Schiff bases are readily accessible in high yield, typically >95%, when aliphatic diamine/aldehyde condensation reactions are carried out under solvent-free conditions or in poly(propyleneglycol) (PPG) as a recyclable reaction medium, with negligible waste.