Problems in Dealing with Electrode Reactions of Larger Molecules

2 Problems in Dealing with Electrode Reactions of Larger Molecules 

More complex molecules may not have the strength for a safe landing when they adsorb but may simply fall to pieces on landing.  

Is the idea of an r.d.s. still useful with the bigger molecules The more the number of steps making up a reaction, the less one step determines the rate of the overall reaction. However, there are sometimes reactions, in which the first step is an electron-transfer reaction, and that may be the slow one, because the adsorbed molecule is so big that the path length that the electron has to travel to the central cities is more than, say, 20 A. Such 

FIGURE 1.18 Formulae of some important amino acids. (From Bockris, J.O M. and Kainthla, R.C., J. Phys. Chem., 84, 2463, 1985.) 

The larger the molecule, the easier it is to take up some alternative pathway. Thus, one starts the reaction with the aim of a certain product, only to find an efficiency of, say, 40%, while 60% goes to, an unwanted pathway. 

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