Peroxides half-wave potentials

Peroxyacetic and peroxybenzoic acids gave reduction waves at 0.00 voltage in the presence of ethylcellulose and methylene blue, but they did not demonstrate a linear relationship between diffusion current and concentration. The acids evidently reacted slowly with the methanol in the solvent, as a continuous decrease in diffusion current was observed with increased time of contact. Peroxyacetic acid showed an additional wave at a half-wave potential of -1.41 V, probably because of the presence of acetic acid, whose half-wave potential was observed to be 1.44 V. Bis(l-hydroxyheptyl)peroxide gave two reduction waves at 0.00 and -1.20 V. A linear relationship existed between the concentration (1 x 10 to 1.3 x lO M) and diffusion current at half-wave potential of -1.20 V, but not at 0.00 voltage. 

In the second group in Table 2.15, two reduction waves were obtained for each of the three peroxides, the first at -0.60 to -0.70 V, the second at -1.0 to -1.26 V. Methyl ethyl ketone peroxide in dimethyl phthalate showed three half-wave potentials, one of which (-1.82 V) was attributed to the phthalate ester, the first reduction wave (0.60 V) was observed only when the concentration of peroxide was below 0.01 M, and the relationship between diffusion current and concentration was nonlinear, since the diffusion current showed a maximum at a concentration of 2.1 x 10 M. The second reduction wave (half-... 

Compounds Peroxide Structure Peroxide content (%) Half-wave potential, (volts)... 

Investigation of the reduction of hydrogen peroxide at a dropping mercuiy electrode commenced early [22], but the question was later [23] examined in more detail. The i-E curves in aqueous solutions for the investigated pH range are characterized by the presence of a single wave with constant slope (b), equal to 0.245 V, on the semi-logarithmic curve. The half-wave potential is approximately —0.79 V... 

From the preliminary research described in the previous section, it appears that the small oxidation wave with half-value potential (EV2) of ca. 0.21V vs. SCE offers favourable perspectives for the amperometric determination of relatively high hydrogen peroxide concentrations. In contrast to the second oxidation wave with I2=0.76 V vs. SCE, the pseudo-limiting currents obtained in the prewave do not satisfy the relation of Levich (Chapter 1, Equationl.15). However, they are almost completely independent of the rotation rate of the electrode, revealing that these limiting currents are not controlled by transport of electroactive species but by (an) other process(es). This is illustrated in Fig.4.5. 

A few typical reactions of l,4-dihydro-l,2,4,5-tetrazines are listed in Scheme 55.1,4-Dihydrotetra-zines (2) are easily oxidized to 1,2,4,5-tetrazines (1) by nitrous acid, nitric acid, oxygen, halogens, iron(III) chloride, hydrogen peroxide, and lead tetraacetate <78HC(33)1077>. In contrast, 1,2,4,5-tetrazines are strong oxidants, as the half wave reduction potentials of Table 4 show. The redox system is quite mobile. 

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