Study of the Electron Transfer Reactions of Organic Anions by Means of Electrochemical and Thermochemical Methods.

点击翻译按钮获取中文摘要

The purpose of the project is to obtain a semiguantitative basis for the structure-reactivity relationship in the reactions of various types of organomagnesium reagents with aromatic carbonyl and nitro substrates. From the previous results, the involvement of electron transfer in all the reactions is suggested on the basis of the formation of by-products due to typical radical processes. The electron-donating abilities(EDA) of some magnesium reagents was also previously estimated by their oxidation peak potentials.Thus, the first plan of this project is to measure electrochemically the reduction potentials of various substrates as the estimate for their electron accepting abilities(EAA). The value of difference(<DETA>E) between the oxidation and reduction potentials of reactants is taken as the estimate for the efficiency of electron transfer in the individual reactions. By means of a polarographic analyzer, the reduction potentials of carbonyl and nitro compounds were measured in THF- … More Bu_4NC10_4 system by use of bis(biphenyl)chromium(I) tetraphenyl borate as internal reference granted by the courtesy of Prof. G. Gritzner, University of Linz. The obtained<DELTA>E value was correlated to the relative yields of normal and abnormal (radical) products in fifteen reactions of magnesium reagents including ArMgBr, ArSMgBr, ArNHMgBr, ArN(MgBr)_2, and AroMgBr.The second plan of the thermochemical study was to apply the exothermal nature of the electron transfer in Grignard reaction established by Prof. T. Holm, Denmark Technical University, to the reactions of our new magnesium reagent having Mg-N-Mg bond. By use of Holm's machine using flow technigue, the plan was unsuccessful because the flow rate applied by him was not suitable for our reaction. However, by use of a batch technigue using a Beckmann's thermo meter, the observed elevation of temperature was almost completely in accord with the classification proposed on the bais of electrochemical measurements.The result is still a preliminary one, and the elaboration of the EDA-EAA concept is in progress: The obtained correlation will contribute to the mechanistic studies. The synthetic applications of various types of magnesium reagents are also in progress. Less