Oxidation-Reduction Potentials

One way to quantify whether a substance is a strong oxidizing agent or a strong reducing agent is to use the oxidation-reduction potential or redox potential. Strong reducing agents can be said to have a high electron-transfer potential. Strong oxidizing agents have low electron-transfer potential. Oxidizing and reducing agents occur as couples, with a strong reducing agent coupled with a weak oxidizing agent and vice versa. Since these processes involve the transfer of electrons, the measurement of the resulting charge separation can be quantified in voltage measured between the couple and a standard hydrogen half-cell with 1 molar hydrogen and 1 atmosphere of hydrogen pressure on it. The redox potential of the hydrogen is zero at pH=0, but for tabulations a pH=7 is used for the hydrogen and under those conditions its redox potential is -0.421 volts.

As a useful

Standard Redox Potentials E'0
Half reaction
 
Half reaction
E'0(V)
Succinate + CO2 + 2H+ +2e-↔α-ketoglutarate + H2O
-0.670
Acetate + 2H+ +2e-↔acetaldehyde
-0.580
2H+ +2e-↔H2
-0.421
α-ketoglutarate + CO2 + 2H+ +2e-↔isocitrate
-0.380
Cystine + 2H+ +2e-↔2 cysteine
-0.340
NAD+ + 2H+ +2e-↔NADH + H+
-0.320
NADP+ + 2H+ +2e-↔NADPH + H+
-0.324
Acetaldehyde + 2H+ +2e-↔ethanol
-0.197
Pyruvate + 2H+ +2e-↔lactate
-0.185
Oxaloacetate + 2H+ +2e-↔malate
-0.166
FAD + 2H+ +2e-↔FADH2
+0.031
Fumarate + 2H+ +2e-↔succinate
+0.031
Ubiquinone + 2H+ +2e-↔ubiquinol
+0.045
2 cytochrome b(ox) +2e-↔2 cytochrome b(red)
+0.070
2 cytochrome c(ox) +2e-↔2 cytochrome c(red)
+0.254
2 cytochrome a3(ox) +2e-↔2 cytochrome a3(red)
+0.385
1/2 O2 + 2H+ +2e-↔H2O
+0.816

This data is from Karp, Table 5.1 for standard conditions

Electrochemistry
 Index

Chemical concepts

Oxidation/
Reduction concepts

 
Chemical concepts 
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