POLAROGRAPHY AS A TOOL FOR INVESTIGATIONS OF CHEMICAL-REACTIONS ACCOMPANYING ELECTRODE PROCESSES

Polarographic investigation of three types of reactions connected with electrode processes is presented. Conjugated acids are in all instanc es reduced more easily (i.e. at more positive potentials) than conjuga ted bases. On the other hand, basic forms are more easily oxidized (at more positive potentials) than conjugated acids. From the current dec rease in this pH range, the rate constant of protonation of the base ( k(r)) can be determined, provided that protonation occurs in a homogen eous solution. Examples of studied systems of this type are given. Ano ther type of chemical reactions preceding the electron transfer are co nversions of covalently hydrated forms into reducible unhydrated speci es. Addition of OH- ions to aldehydes results in geminal diol anions ( RCH(OHO-) which can be oxidized to carboxylic acids. Examples of chemi cal reactions interposed between two electron transfers are reactions of arylhydroxylamines formed in a four-electron reduction of nitro aro matic compounds. The roles of protonation, dehydration, condensation a nd some deactivation reactions of arylhydroxylamines are discussed.