โ Scribed by P. Zuman
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Polarography has been used in investigations of equilibria between carbonyl compounds and Schiff bases. Formation of mercury compounds of thiols, some urea, and thiourea derivatives is manifested by anodic polarographic waves. Electrochemical data for numerous organic compounds can be correlated with structural parameters using LFERs. Such correlations can be used in mechanistic studies and in choice of representative model compounds. For organic compounds bearing two electroactive centers the degree of their mutual interaction is reflected by their electrochemical behavior. Such interactions range from weak to medium strength (manifested by substituent effects) to strong interactions (resulting in changes in mechanisms of electrode processes). Strong interactions may result in reversal of the sequence of the reducibility of the two electroactive groups. Changes of polarographic current-voltage curves with solution composition enable determination of equilibrium constants for rapidly and slowly established equilibria preceding electron transfer. From currents governed by homogeneous antecedent reactions rate constants of fast reactions (between 10 4 and 10 10 l mol 01 s 01 ) can be obtained. For slower reactions occurring in the bulk of the solution variations of currents with time are used in kinetic studies. Polarographic measurements can be carried out directly in the reaction mixture and are complementary to spectrophotometry. Kinetics can be followed polarographically even in heterogeneous systems. This was used in studies of formation of slightly soluble complexes, e.g., of heavy metal ions with BAL and bile salts. Adsorption of organic (e.g., pesticides) and inorganic species on lignin can be followed, as well as formation of aromatic aldehydes and unsaturated ketones in alkaline cleavage of lignin. Examples of practical applications of polarographic analysis in food chemistry and pharmaceutical and medical science are given. แญง 1997 Academic Press Contents Introduction. Anodic waves of organic species corresponding to a formation of mercury compounds. Applications of linear free energy relationships. Compounds with two electroactive centers. Chemical reactions accompanying the electrode process. Polarography in the study of homogeneous reactions. Polarography in investigations of heterogeneous systems. Practical applications of polarography. Conclusions.
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