Study of first order chemical reaction following charge transfer using the double potential-step chronocoulometric method: II. Experimental study of reactions inactivating the product of the charge transfer reaction — Derivatives of tetrahydropterins as a model system

The theory of double-step chronocoulometry has been verified for the e.c. electrode reaction type, a reversible electron transfer being followed by a chemical reaction in solution leading to inactivation of the primary product. In contrast to methods proposed previously, the inactivation reaction rate constants were calculated using the charge values obtained by integration up to current decay after the second potential step. The anodic oxidation of tetrahydropterin derivatives on a Pt electrode was employed as a model system. It has been found that the rate of inactivation of the anodic product decreases with increasing pH of the solution and is different for various derivatives studied. A special case of zero inactivation rate was verified using the Fe³⁺/Fe²⁺ redox system in an acidic medium.