Oxidation-Reduction Potentials

氧化还原电势

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.

衡量一种物质是强氧化剂还是强还原剂的一种方法是使用氧化还原电势或氧化还原势。强还原剂可以被认为具有较高的电子转移势。强氧化剂则具有较低的电子转移势。氧化剂和还原剂以偶对形式存在，强还原剂与弱氧化剂偶对，反之亦然。由于这些过程涉及电子的转移，因此可以量化由此产生的电荷分离，通过测量偶对与标准氢半电池之间的电压来实现，该标准氢半电池具有1摩尔浓度的氢和1大气压的氢气。氢的氧化还原电势在pH=0时为零，但在表格中通常使用pH=7的条件，此时其氧化还原电势为-0.421伏特。

As a useful reference, the redox potentials of couples that commonly occur in biochemistry can give insight into their roles in biological energy processes. A negative number for this potential indicates a reducing agent whereas a strong oxidizer will have a positive redox potential. Since the obtaining of useful energy in a biological process generally involves oxidation of some foodstuff, it follows that a large negative redox potential like -0.32 V for NAD⁺ suggests a useful role in producing a reduced product, like NADH. A reduced coenzyme NADH can be oxidized to provide energy for biological processes.

作为有用的参考，生物化学中常见的氧化还原电对的电势可以提供关于它们在生物能量过程中的作用的见解。该电势的负数表明它是还原剂，而强氧化剂则具有正的氧化还原电势。由于生物过程中获得有用能量通常涉及某些营养物质的氧化，因此像NAD+的-0.32 V这样的大负电势表明其在产生还原产物（如NADH）中具有重要作用。还原型辅酶NADH可以被氧化以提供生物过程所需的能量。

Standard Redox Potentials E^'₀ 标准还原电势 E'⁰
Half reaction 半反应		Half reaction 半反应	E^'₀(V)
Succinate + CO₂ + 2H⁺ +2e^- 琥珀酸 + CO₂ + 2H⁺ + 2e⁻	↔	α-ketoglutarate + H₂O α-酮戊二酸 + H₂O	-0.670
Acetate + 2H⁺ +2e^- 醋酸根 + 2H⁺ + 2e⁻	↔	acetaldehyde 乙醛	-0.580
2H⁺ +2e^-	↔	H₂	-0.421
α-ketoglutarate + CO₂ + 2H⁺ +2e^- α-酮戊二酸 + CO₂ + 2H⁺ + 2e⁻	↔	isocitrate 异柠檬酸	-0.380
Cystine + 2H⁺ +2e^- 胱氨酸 + 2H⁺ + 2e⁻	↔	2 cysteine 2 cysteine	-0.340
NADP⁺ + 2H⁺ +2e^- NADP⁺ + 2H⁺ + 2e⁻	↔	NADPH + H⁺ NADPH + H⁺	-0.324
NAD⁺ + 2H⁺ +2e^- NAD⁺ + 2H⁺ + 2e⁻	↔	NADH + H⁺ NADH + H⁺	-0.320
Acetaldehyde + 2H⁺ +2e^- 乙醛 + 2H⁺ + 2e⁻	↔	ethanol 乙醇	-0.197
Pyruvate + 2H⁺ +2e^- 丙酮酸 + 2H⁺ + 2e⁻	↔	lactate 乳酸	-0.185
Oxaloacetate + 2H⁺ +2e^- 草酰乙酸 + 2H⁺ + 2e⁻	↔	malate 苹果酸	-0.166
FAD + 2H⁺ +2e^- FAD + 2H⁺ + 2e⁻	↔	FADH₂ FADH₂	+0.031
Fumarate + 2H⁺ +2e^- 琥珀酸 + 2H⁺ + 2e⁻	↔	succinate 琥珀酸	+0.031
Ubiquinone + 2H⁺ +2e^- ubiquinone + 2H⁺ + 2e⁻	↔	ubiquinol ubiquinol（专名或术语）	+0.045
2 cytochrome b_(ox) +2e^- 2个细胞色素b（氧化态）+2e -	↔	2 cytochrome b_(red) 2 细胞色素 b (红)	+0.070
2 cytochrome c_(ox) +2e^- 2 细胞色素 c（氧化型） + 2e -	↔	2 cytochrome c_(red) 2 细胞色素 c (还原型)	+0.254
2 cytochrome a_3(ox) +2e^- 2 cytochrome a 3(ox) + 2e -	↔	2 cytochrome a_3(red) 2 cytochrome a 3(红色)	+0.385
1/2 O₂ + 2H⁺ +2e^-	↔	H₂O	+0.816

This data is from Karp, Table 5.1 for

这些数据来自Karp的表5.1，标准条件

standard conditions

Electrochemistry

电化学

Index

Chemical concepts

Oxidation/
Reduction concepts

Reference
Karp
Ch 5

索引化学概念氧化/还原概念参考 Karp 第5章

HyperPhysics*****Chemical concepts

HyperPhysics ***** 化学概念

R Nave

Go Back