Chemical coupled homogeneous

Fig. 13. Diagnostic plots for electrode reactions with coupled homogeneous reactions, illustrated for the RDE. (a) CE mechanism. Curve A, no effect from chemical reaction (5k = 0) curve B, effect of preceding chemical reaction (5k >0). (b) Catalytic mechanism. Curve A, in the absence of parallel chemical reaction curve B, experimental dependence predicted from eqn. (175).

Reversible, quasi-reversible and irreversible electrode processes have been studied at the RDE [266] as have coupled homogeneous reactions without [267] and with the effect of electrode kinetics [268], The theoretical results are very similar to those of a.c. polarography, being very phase-angle sensitive to coupled chemical reactions in the rotation speed range where convection can be neglected, the polarographic results may be directly applied [269]. 

Double step chronocoulometry also gives information on the kinetics of coupled homogeneous reactions8. For example, any deviation, under diffusion control, from (10.35) and (10.36) implies a chemical complication, which can be compared with the responses for the various possible mechanisms. 

Coupled homogeneous reactions in electrochemistry — Chemical reactions occurring in an electrochemical cell, in which the electroactive compounds undergo chemical transformation by reacting with the electroinactive compounds, are known as coupled homogeneous reactions. All the compounds in the system are present together in the same phase - EC, CE, and EC reactions. 

Coupled homogeneous chemical reactions 82 Theoretical modelling 83... 

The internal chemical coupling C-+C includes homogeneous reactions in a gaseous or aqueous phase, and transport processes driven by chemical forces, such as molecular or ionic diffusion, and those heterogeneous processes related to it that do not involve large-scale transport for example, certain types of surface reactions or interactions between particles in colloidal suspensions (O Melia, Chapter 16, this volume) that are driven primarily by electrochemical forces fall in the class of C->C interactions. 

Many interesting processes occurring at the liquid/liquid interface involve coupled homogeneous chemical reactions. In principle, electrochemical methods used for probing complicated mechanisms at metal electrodes (61) can be employed at the ITIES. However, many of these techniques (e.g., rotating ring-disk electrode or fast-scan cyclic voltammetry) are hard to adapt to liquid/liquid measurements. Because of technical problems, few studies of multistep processes at the ITIES have been reported to date (1,62). 

We have seen in this section how microelectrodes can be used in a variety of ways to study both coupled homogeneous chemical reactions and heterogeneous electron transfers. We have also seen one example of a study of metal deposition. The development of microelectrodes has made possible... 

Let us first consider briefly how the use of mass transport as a variable can provide a guide to the reaction mechanism and give quantitative kinetic detail. As an illustration, we consider the behaviour of CE and EC processes (where E signifies electron transfer and C represents a chemical step) at a rotating disc electrode (RDE). This hydrodynamic system has already been discussed by Albery et al. and the reader is referred to Chap. 4 for details. CE and EC processes represent the simplest conceivable electrode reactions involving coupled homogeneous kinetics mechanistic examples of both types are shown in Table 1. In the discussion which follows, the electron-transfer reaction in the two mechanisms is considered to be a cathodic process the extension to the anodic case is trivial. 

Electrode kinetics and coupled homogeneous kinetics the measurement of the rate of fast chemical reactions... 

A similar treatment can be given for other chemical reactions coupled to the charge-transfer reaction (4). This approach is often useful in formulating a qualitative or semi-quantitative interpretation of i-E curves. Notice, however, that unless explicit expressions for mR and p can be given in a particular case, the exact values of k cannot be determined. The rigorous treatment of electrode reactions with coupled homogeneous chemical reactions is discussed in Chapter 12. 

ELECTRODE REACTIONS WITH COUPLED HOMOGENEOUS CHEMICAL REACTIONS... 

Chapter 12. Electrode Reactions with Coupled Homogeneous Chemical Reactions... 

Chapter 12. Electrode Reactions with Coupled Homogeneous Chemical Reactions TABLE 12.1.1 Approximate Time Windows for Different Electrochemical Techniques... 

Several Different Coupled Homogeneous Chemical Reactions in Voltammetry... 

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