Polarographic Behavior of Glycol Dimercaptoacetate
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概要
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Polarographic behaviour of glycol dimercaptoacetate has been studied in 25% ethanol at d.m.e. in the pH range 1.56–11.56 in presence of 0.1 M KNO<SUB>3</SUB>. In the acidic media, the current-voltage curves consist of three waves; a prewave due to the adsorption of anodic reaction product at the mercury drop surface, main anodic wave due to the electroxidation of –SH groups and a third wave at more positive potential due to the insoluble film formation on the electrode surface whose solubility depends on pH of the solution. In the alkaline media only two waves, a prewave and the main anodic wave, are observed. The effects of various factors such as different buffer, Hg-pressure, temperature, ethanol and depolarizer concentrations on the wave characteristics have been investigated. The electrode reaction is irreversible at higher pH but in acid media it is reversible and diffusion controlled involving a two electron transfer process, with the formation of (<U>Remark: Graphics omitted.</U>) complex. The overall dissociation constant (p<I>K</I>) of the sulphydryl groups has been found to be 8.20 at 20 °C. At pH 4.80, the maximum number of moles adsorbed on unit area is 6.83×10<SUP>−10</SUP>mol/cm<SUP>2</SUP> <I>i.e.</I> 4.12×10<SUP>14</SUP> molecule/ cm<SUP>2</SUP>. Adsorption coefficient and molar adsorption energy are calculated to be 1.445×10<SUP>4</SUP> and 31.2 kcal/gm mol respectively. The respective values of kinetic parameters, <I>viz.</I> transfer coefficient (α) and formal rate constant (<I>K</I><SUP>°</SUP><SUB>b.h</SUB>) for the irreversible wave at pH 11.56 are 0.76 and 2.6×10<SUP>−9</SUP> cm/s.
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