Electrochemical Studies Of The Radicals Of Alcohols

Alcohols as solvent, material for synthesis have been widely used. Recently, they as high-performance and low-pollution fuel have been received more and more attention. Therefore, studies on oxidation process of alcohols and thermodynamics of their oxidation intermediate radicals are of significance for making full use of them. For this purpose, current approaches have been established in alcohols I peroxydisulfate / water system. Among these approaches, sulfate radical anion SO4~ was produced by photolysis, thermolysis or through chemical reduction of peroxydisulfate ion S208 2- by low-valent transition metal ions. The S04 initiated a radical-chain reaction that both S208 2- and S04 oxidizing alcohols to the corresponding aldehyde or ketone via intermediate radical in bulk solution. The intermediate radicals of alcohols in the radical-chain reaction were detected by electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopies. In addition, it is known that alcohols can be directly oxidized on solid electrode such as platinum or glass carbon electrodes at positive potential to produce their oxidation waves. However, the oxidation wave referred to overall oxidation process from original alcohol to final product, any information about the radicals during oxidation of alcohols was not obtained. In this work, the radicals of alcohols had been detected by voltammetry based on their reduction waves on mercury electrode in alcohols I peroxydisulfate / phosphate buffer solution. Both generation and reduction process of the radicals of alcohols were studied. Part 1 The achievement of the studies on the sulfate radical was reviewed with 42 III references. Part 2 In this work, both generation and reduction process of the (i-radicals of lower fatty alcohols were studied by voltanimetry in lower fatty alcohols I peroxydisulfate / phosphate buffer system. Experimental results showed that such three reactions were successively completed at negative potential on mercury electrode surface as: (1) sulfate radical anion S04 was generated electrochemically from one-electron reduction of peroxydisulfate ion s2o~ 2-, (2) the S04 oxidized lower fatty alcohols to the corresponding (i-radicals and (3) the (i-radicals were reduced in one-electron and one-proton addition to produce their own reduction waves. The apparent free energy tX~Gm of the (i-radicals of lower straight-chain fatty alcohols such as methanol, ethanol, propanol, butanol and pentanol obtained were 107.09, 116.74, 122.53, 126.39 and 129.28 KJ mol/L, respectively. The proposed method is more simple and convenient than current approaches based on the radical-chain reaction for studying alcohol oxidation. Part 3 Benzyl alcohol was rapidly oxidized to electroactive benzaldehyde through radical-chain reaction initiated by sulfate radical S04 electrogenerated from reduction of S2082. The produced benzaldehyde was reduced via intermediate free radical. The free radical of benzaldehyde was oxidized by both S7082 and S04. to produce a catalytic wave. Based on this, a novel method for the determination of benzyl alcohol was proposed. In 0.1 mol/L KH2PQ4 +Na2HPO4 buffer (pH5.6?.1) ?.OxlO2molIL K2S208 solution, second-order derivative peak current of t...