| The aim of this Thesis was an understanding of the electrochemical behavior of various carbonyl compounds as well as investigation of reaction mechanisms of some chemical reactions of these carbonyl compounds. This was achieved by using polarography as an electroanalytical tool. The goal of this Thesis is to contribute to the research dealing with basic organic electrochemistry and to show that polarography can still assist in solving of complex scientific problems. Hence, the electrochemical behavior of benzaldehyde, three isomeric phthalaldehydes and some aryl hydrazones have been studied by using polarography. UV spectroscopy was sometimes used to support electrochemical results.; The electrochemical behavior of three isomeric benzenedicarboxaldehydes---orthophthalaldehyde, isophthalaldehyde and terephthalaldehyde---differs considerably. The observed differences are partly due to variations in their solution chemistry, particularly hydration and protonation, partly by the role of sequences of chemical and electrochemical steps.; Changes of polarographic curves with time were used in investigations of reactions of benzaldehyde and terephthalaldehyde with hydrazine over a wide pH-range. In the reaction between benzaldehyde and hydrazine it was possible to provide direct experimental evidence for the formation of carbinolamine intermediate and to follow the kinetics and equilibria involved. The reaction between terephthalaldehyde and hydrazine has been studied less extensively as it is complicated by a 15% hydration of one CHO group. Furthermore, hydrazine can react with both aldehydic groups in para positions. Hence, more than one carbinolamine intermediate can be formed yielding monohydrazone as intermediate and a dihydrazone as final product.; In order to interpret correctly the polarographic behavior of hydrazones obtained in the reaction of hydrazine with benzaldehyde and terephthalaldehyde, the electroreduction of some hydrazones has been revisited. In electrochemical literature it was generally assumed that reduction of hydrazones at pH below about 7 takes place in a monoprotonated form. Our polarographic investigations proved that at pH < 7 a diprotonated form of the hydrazone is reduced. This diprotonated form is generated as a reactive intermediate at the electrode surface. By using comparison of the reduction of fluorenone imine (which is stable between pH 6 and 10) with that of fluorenone hydrazone and that of fluorenone N,N,N-trimethylhydrazonium ion, it was possible to confirm the formation of an Mine as a reactive intermediate. |
