# Redox > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Redox > Markdown URL: https://mediated.wiki/source/Redox.md > Source: https://en.wikipedia.org/wiki/Redox > Source revision: 1349288186 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) Chemical reaction with oxidation state changes For other uses, see [Redox (disambiguation)](/source/Redox_(disambiguation)). [Sodium](/source/Sodium) "gives" one outer electron to [fluorine](/source/Fluorine), bonding them to form [sodium fluoride](/source/Sodium_fluoride). The sodium atom is oxidized, and fluorine is reduced. When a few drops of [glycerol](/source/Glycerol) (mild reducing agent) are added to powdered [potassium permanganate](/source/Potassium_permanganate) (strong oxidizing agent), a violent redox reaction accompanied by self-ignition starts. Example of a reduction–oxidation reaction between sodium and chlorine, with the *OIL RIG* mnemonic[1] **Redox** ([/ˈrɛdɒks/](https://en.wikipedia.org/wiki/Help:IPA/English) [*RED-oks*](https://en.wikipedia.org/wiki/Help:Pronunciation_respelling_key), [/ˈriːdɒks/](https://en.wikipedia.org/wiki/Help:IPA/English) [*REE-doks*](https://en.wikipedia.org/wiki/Help:Pronunciation_respelling_key), **reduction–oxidation**[2] or **oxidation–reduction**[3]: 150) is a type of [chemical reaction](/source/Chemical_reaction) in which the [oxidation states](/source/Oxidation_state) of the [reactants](/source/Reactant) change.[4] Oxidation is the loss of [electrons](/source/Electron) or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction. There are two classes of redox reactions: - [Electron transfer](/source/Electron_transfer) – Only one (usually) electron flows from the atom, ion, or molecule being oxidized to the atom, ion, or molecule that is reduced. This type of redox reaction is often discussed in terms of redox couples and electrode potentials. - Atom transfer – An atom transfers from one [substrate](/source/Substrate_(chemistry)) to another. For example, in the [rusting](/source/Rusting) of [iron](/source/Iron), the oxidation state of iron atoms increases as the iron converts to an [oxide](/source/Oxide), and simultaneously, the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are commonly associated with forming oxides, other chemical species can serve the same function.[5] In [hydrogenation](/source/Hydrogenation), bonds like [C=C](/source/Alkene) are reduced by [transfer of hydrogen atoms](/source/Transfer_hydrogenation). ## Terminology "Redox" is a [portmanteau](/source/Portmanteau) of "reduction" and "oxidation". The term was first used in a 1928 article by [Leonor Michaelis](/source/Leonor_Michaelis) and [Louis B. Flexner](/source/Louis_B._Flexner).[6][7] Oxidation is a process in which a substance loses electrons. Reduction is a process in which a substance gains electrons. The processes of oxidation and reduction occur simultaneously and cannot occur independently.[5] In redox processes, the reductant transfers electrons to the oxidant. Thus, in the reaction, the reductant or [reducing agent](/source/Reducing_agent) loses electrons and is oxidized, and the oxidant or [oxidizing agent](/source/Oxidizing_agent) gains electrons and is reduced. The pair of an oxidizing and reducing agent that is involved in a particular reaction is called a redox pair. A redox couple is a reducing species and its corresponding oxidizing form,[8] e.g., [Fe2+](/source/Iron)/ [Fe3+](/source/Iron).The oxidation alone and the reduction alone are each called a *[half-reaction](/source/Half-reaction)* because two half-reactions always occur together to form a whole reaction.[5] In [electrochemical reactions](/source/Electrochemistry) the oxidation and reduction processes do occur simultaneously but are separated in space. ### Oxidants Main article: [Oxidizing agent](/source/Oxidizing_agent) The [international](/source/Globally_Harmonized_System_of_Classification_and_Labeling_of_Chemicals) [pictogram](/source/GHS_hazard_pictograms) for oxidizing chemicals Oxidation originally implied a reaction with oxygen to form an oxide. Later, the term was expanded to encompass [substances](/source/Chemical_substance) that accomplished chemical reactions similar to those of oxygen. Ultimately, the meaning was generalized to include all processes involving the loss of electrons or the increase in the oxidation state of a chemical species.[9]: A49 Substances that have the ability to oxidize other substances (cause them to lose electrons) are said to be oxidative or oxidizing, and are known as oxidizing agents, oxidants, or oxidizers. The oxidant removes electrons from another substance, and is thus itself reduced.[9]: A50 Because it "accepts" electrons, the oxidizing agent is also called an [electron acceptor](/source/Electron_acceptor). Oxidants are usually chemical substances with elements in high oxidation states[3]: 159 (e.g., [N 2O 4](/source/Dinitrogen_tetroxide), [MnO− 4](/source/Permanganate), [CrO 3](/source/Chromium_trioxide), [Cr 2O2− 7](/source/Dichromate), [OsO 4](/source/Osmium(VIII)_oxide)), or else highly [electronegative](/source/Electronegativity) elements (e.g. [O2](/source/Oxygen), [F2](/source/Fluorine), [Cl2](/source/Chlorine), [Br2](/source/Bromine), [I2](/source/Iodine)) that can gain extra electrons by oxidizing another substance.[3]: 909 Oxidizers are oxidants, but the term is mainly reserved for sources of oxygen, particularly in the context of explosions. [Nitric acid](/source/Nitric_acid) is a strong oxidizer.[10] ### Reductants Main article: [Reducing agent](/source/Reducing_agent) Substances that have the ability to reduce other substances (cause them to gain electrons) are said to be reductive or reducing and are known as reducing agents, reductants, or reducers. The reductant transfers electrons to another substance and is thus itself oxidized.[3]: 159 Because it donates electrons, the reducing agent is also called an [electron donor](/source/Electron_donor). Electron donors can also form [charge transfer complexes](/source/Charge_transfer_complex) with electron acceptors. The word reduction originally referred to the loss in weight upon heating a metallic [ore](/source/Ore) such as a [metal oxide](/source/Metal_oxide) to extract the metal. In other words, ore was "reduced" to metal.[11] [Antoine Lavoisier](/source/Antoine_Lavoisier) demonstrated that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the metal atom gains electrons in this process. The meaning of reduction then became generalized to include all processes involving a gain of electrons.[11] Reducing equivalent refers to [chemical species](/source/Chemical_species) which transfer the equivalent of one [electron](/source/Electron) in redox reactions. The term is common in [biochemistry](/source/Biochemistry).[12] A reducing equivalent can be an electron or a hydrogen atom as a [hydride ion](/source/Hydrogen_anion).[13] Reductants in chemistry are very diverse. [Electropositive](/source/Electropositive) elemental [metals](/source/Metal), such as [lithium](/source/Lithium), [sodium](/source/Sodium), [magnesium](/source/Magnesium), [iron](/source/Iron), [zinc](/source/Zinc), and [aluminium](/source/Aluminium), are good reducing agents. These metals donate electrons relatively readily.[14] [Hydride transfer reagents](https://en.wikipedia.org/w/index.php?title=Hydride_transfer_reagents&action=edit&redlink=1), such as [NaBH4](/source/Sodium_borohydride) and [LiAlH4](/source/Lithium_aluminium_hydride), reduce by atom transfer: they transfer the equivalent of hydride or H−. These reagents are widely used in the reduction of [carbonyl](/source/Carbonyl) compounds to [alcohols](/source/Alcohols).[15][16] A related method of reduction involves the use of hydrogen gas (H2) as sources of H atoms.[3]: 288 ### Electronation and de-electronation The [electrochemist](/source/Electrochemistry) [John Bockris](/source/John_Bockris) proposed the words electronation and de-electronation to describe reduction and oxidation processes, respectively, when they occur at [electrodes](/source/Electrode).[17] These words are analogous to [protonation](/source/Protonation) and [deprotonation](/source/Deprotonation).[18] [IUPAC](/source/IUPAC) has recognized the terms electronation[19] and de-electronation.[20] ## Rates, mechanisms, and energies This section needs expansion. You can help by adding missing information. (April 2023) Redox reactions can occur slowly, as in the formation of [rust](/source/Rust), or rapidly, as in the case of burning [fuel](/source/Fuel). Electron transfer reactions are generally fast, occurring within the time of mixing.[21] The mechanisms of atom-transfer reactions are highly variable because many kinds of atoms can be transferred. Such reactions can also be quite complex, involving many steps. The mechanisms of electron-transfer reactions occur by two distinct pathways, [inner sphere electron transfer](/source/Inner_sphere_electron_transfer)[22] and [outer sphere electron transfer](/source/Outer_sphere_electron_transfer).[23] Analysis of bond energies and [ionization energies](/source/Ionization_energy) in water allows calculation of the thermodynamic aspects of redox reactions.[24] ## Standard electrode potentials (reduction potentials) Each half-reaction has a standard [electrode potential](/source/Electrode_potential) (*E*o cell), which is equal to the potential difference or [voltage](/source/Voltage) at equilibrium under [standard conditions](/source/Standard_state) of an [electrochemical cell](/source/Electrochemical_cell) in which the [cathode](/source/Cathode) reaction is the [half-reaction](/source/Half-reaction) considered, and the [anode](/source/Anode) is a [standard hydrogen electrode](/source/Standard_hydrogen_electrode) where hydrogen is oxidized:[25] - 1⁄2 H2 → H+ + e− The electrode potential of each half-reaction is also known as its reduction potential (*E*o red), or potential when the half-reaction takes place at a cathode. The reduction potential is a measure of the tendency of the oxidizing agent to be reduced. Its value is zero for H+ + e− → 1⁄2H2 by definition, positive for oxidizing agents stronger than H+ (e.g., +2.866 V for F2) and negative for oxidizing agents that are weaker than H+ (e.g., −0.763V for Zn2+).[9]: 873 For a redox reaction that takes place in a cell, the potential difference is: - *E*o cell = *E*o cathode − *E*o anode However, the potential of the reaction at the anode is sometimes expressed as an *oxidation potential*: - *E*o ox = −*E*o red The oxidation potential is a measure of the tendency of the reducing agent to be oxidized but does not represent the physical potential at an electrode. With this notation, the cell voltage equation is written with a plus sign - *E*o cell = *E*o red(cathode) + *E*o ox(anode) ## Examples of redox reactions Illustration of a redox reaction In the reaction between [hydrogen](/source/Hydrogen) and [fluorine](/source/Fluorine), hydrogen is being oxidized and fluorine is being reduced: - H2 + F2 → 2 HF This spontaneous reaction releases a large amount of energy (542 kJ per 2 g of hydrogen) because two H-F bonds are much stronger than one H-H bond and one F-F bond.[26] This reaction can be analyzed as two [half-reactions](/source/Half-reaction). The oxidation reaction converts hydrogen to [protons](/source/Proton): - H2 → 2 [H+](/source/Hydrogen_ion) + 2 [e−](/source/Electron) The reduction reaction converts [fluorine](/source/Fluorine) to the fluoride anion: - F2 + 2 e− → 2 [F−](/source/Fluoride) The half-reactions are combined so that the electrons cancel: - H 2 → 2 H+ + 2 e− F 2 + 2 e− → 2 F− H2 + F2 → 2 H+ + 2 F− The protons and fluoride combine to form [hydrogen fluoride](/source/Hydrofluoric_acid) in a non-redox reaction: - 2 H+ + 2 F− → 2 HF The overall reaction is: - H2 + F2 → 2 HF ### Metal displacement A redox reaction is the force behind an [electrochemical cell](/source/Electrochemical_cell) like the [Galvanic cell](/source/Galvanic_cell) pictured. The battery is made out of a zinc electrode in a ZnSO4 solution connected with a wire and a porous disk to a copper electrode in a CuSO4 solution. In this type of reaction, a [metal](/source/Metal) atom in a compound or solution is replaced by an atom of another metal. For example, [copper](/source/Copper) is deposited when [zinc](/source/Zinc) metal is placed in a [copper(II) sulfate](/source/Copper(II)_sulfate) solution: - Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s) In the above reaction, zinc metal displaces the copper(II) ion from the copper sulfate solution, thus liberating free copper metal. The reaction is spontaneous and releases 213 kJ per 65 g of zinc. The ionic equation for this reaction is: - Zn + Cu2+ → Zn2+ + Cu As two [half-reactions](/source/Half-reaction), it is seen that the zinc is oxidized: - Zn → Zn2+ + 2 e− And the copper is reduced: - Cu2+ + 2 e− → Cu ### Other examples - The reduction of [nitrate](/source/Nitrate) to [nitrogen](/source/Nitrogen) in the presence of an acid ([denitrification](/source/Denitrification)): - - 2 NO−3 + 10 e− + 12 H+ → N2 + 6 H2O - The [combustion](/source/Combustion) of [hydrocarbons](/source/Hydrocarbon), such as in an [internal combustion engine](/source/Internal_combustion_engine), produces [water](/source/Water), [carbon dioxide](/source/Carbon_dioxide), some partially oxidized forms such as [carbon monoxide](/source/Carbon_monoxide), and heat [energy](/source/Energy). Complete oxidation of materials containing [carbon](/source/Carbon) produces carbon dioxide. - The stepwise oxidation of a hydrocarbon by oxygen, in [organic chemistry](/source/Organic_chemistry), produces water and, successively: an [alcohol](/source/Alcohol_(chemistry)), an [aldehyde](/source/Aldehyde) or a [ketone](/source/Ketone), a [carboxylic acid](/source/Carboxylic_acid), and then a [peroxide](/source/Peroxide). ### Corrosion and rusting Oxides, such as [iron(III) oxide](/source/Iron(III)_oxide) or [rust](/source/Rust), which consists of hydrated [iron(III) oxides](/source/Iron(III)_oxide) Fe2O3·*n*H2O and [iron(III) oxide-hydroxide](/source/Iron(III)_oxide-hydroxide) (FeO(OH), Fe(OH)3), form when oxygen combines with other elements. Iron rusting in [pyrite](/source/Pyrite) cubes - The term [corrosion](/source/Corrosion) refers to the electrochemical oxidation of metals in reaction with an oxidant such as oxygen. [Rusting](/source/Rust), the formation of [iron oxides](/source/Iron_oxide), is a well-known example of electrochemical corrosion: it forms as a result of the oxidation of [iron](/source/Iron) metal. Common rust often refers to [iron(III) oxide](/source/Iron(III)_oxide), formed in the following chemical reaction: - - 4 Fe + 3 O2 → 2 Fe2O3 - The oxidation of iron(II) to iron(III) by [hydrogen peroxide](/source/Hydrogen_peroxide) in the presence of an [acid](/source/Acid): - - Fe2+ → Fe3+ + e− - H2O2 + 2 e− → 2 OH− - Here the overall equation involves adding the reduction equation to twice the oxidation equation, so that the electrons cancel: - 2 Fe2+ + H2O2 + 2 H+ → 2 Fe3+ + 2 H2O ### Disproportionation A [disproportionation](/source/Disproportionation) reaction is one in which a single substance is both oxidized and reduced. For example, [thiosulfate](/source/Thiosulfate) ion with sulfur in oxidation state +2 can react in the presence of acid to form elemental sulfur (oxidation state 0) and [sulfur dioxide](/source/Sulfur_dioxide) (oxidation state +4). - S2O2−3 + 2 H+ → S + SO2 + H2O Thus one sulfur atom is reduced from +2 to 0, while the other is oxidized from +2 to +4.[9]: 176 ## Redox reactions in industry [Cathodic protection](/source/Cathodic_protection) is a technique used to control the corrosion of a metal surface by making it the [cathode](/source/Cathode) of an [electrochemical cell](/source/Electrochemical_cell). A simple method of protection connects protected metal to a more easily corroded "[sacrificial anode](/source/Sacrificial_anode)" to act as the [anode](/source/Anode). The sacrificial metal, instead of the protected metal, then corrodes. Oxidation is used in a wide variety of industries, such as in the production of [cleaning products](https://en.wikipedia.org/wiki/Category:Cleaning_products) and oxidizing [ammonia](/source/Ammonia) to produce [nitric acid](/source/Nitric_acid).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] Redox reactions are the foundation of electrochemical cells, which can generate electrical energy or support [electrosynthesis](/source/Electrosynthesis). Metal [ores](/source/Ore) often contain metals in oxidized states, such as oxides or sulfides, from which the pure metals are extracted by [smelting](/source/Smelting) at high temperatures in the presence of a reducing agent. The process of [electroplating](/source/Electroplating) uses redox reactions to coat objects with a thin layer of a material, as in [chrome-plated](/source/Chrome_plating) [automotive](/source/Automotive) parts, [silver plating](/source/Plating#Silver_plating) [cutlery](/source/Cutlery), [galvanization](/source/Galvanization) and [gold-plated](/source/Gold-plated) [jewelry](/source/Jewelry).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] ## Redox reactions in biology This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2023) (Learn how and when to remove this message) [Enzymatic browning](/source/Food_browning#Enzymatic_browning) is an example of a redox reaction that takes place in most fruits and vegetables. [Ascorbic acid](/source/Ascorbic_acid) ([reduced form](/source/Reducing_agent) of [vitamin C](/source/Vitamin_C)) [Dehydroascorbic acid](/source/Dehydroascorbic_acid) ([oxidized form](/source/Oxidizing_agent) of vitamin C) Many essential [biological](/source/Biology) processes involve redox reactions. Before some of these processes can begin, iron must be [assimilated](/source/Assimilation_(biology)) from the environment.[27] [Aerobic cellular respiration](/source/Cellular_respiration), for instance, is the oxidation of substrates [in this case: [glucose](/source/Glucose) (C6H12O6)] and the reduction of [oxygen](/source/Oxygen) to [water](/source/Water). The summary equation for aerobic respiration is: - C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] The process of cellular respiration also depends heavily on the reduction of [NAD+](/source/Nicotinamide_adenine_dinucleotide) to NADH and the reverse reaction (the oxidation of NADH to NAD+). [Photosynthesis](/source/Photosynthesis) and cellular respiration are complementary, but photosynthesis is not the reverse of the redox reaction in cellular respiration: - 6 CO2 + 6 H2O + [light energy](/source/Photon) → C6H12O6 + 6 O2 [Biological energy](/source/Biological_energy) is frequently stored and released using redox reactions. Photosynthesis involves the reduction of [carbon dioxide](/source/Carbon_dioxide) into [sugars](/source/Sugar) and the oxidation of [water](/source/Water_(molecule)) into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce [nicotinamide adenine dinucleotide](/source/Nicotinamide_adenine_dinucleotide) (NAD+) to NADH, which then contributes to the creation of a [proton gradient](/source/Proton_gradient), which drives the synthesis of [adenosine triphosphate](/source/Adenosine_triphosphate) (ATP) and is maintained by the reduction of oxygen. In animal cells, [mitochondria](/source/Mitochondria) perform similar functions. See also: [Membrane potential](/source/Membrane_potential) The term *redox state* is often used to describe the balance of [GSH/GSSG](/source/Glutathione), NAD+/NADH and [NADP+/NADPH](/source/Nicotinamide_adenine_dinucleotide_phosphate) in a biological system such as a [cell](/source/Cell_(biology)) or [organ](/source/Organ_(biology)). The redox state is reflected in the balance of several sets of metabolites (e.g., [lactate](/source/Lactic_acid) and [pyruvate](/source/Pyruvate), [beta-hydroxybutyrate](/source/Beta-hydroxybutyrate) and [acetoacetate](/source/Acetoacetate)), whose interconversion is dependent on these ratios. Redox mechanisms also control some cellular processes. Redox proteins and their genes must be co-located for redox regulation according to the [CoRR hypothesis](/source/CoRR_hypothesis) for the function of [DNA](/source/DNA) in [mitochondria](/source/Mitochondrion) and [chloroplasts](/source/Chloroplast). ### Redox cycling Wide varieties of [aromatic compounds](/source/Aromaticity) are [enzymatically](/source/Enzyme) reduced to form [free radicals](/source/Radical_(chemistry)) that contain one more electron than their parent compounds. In general, the electron donor is any of a wide variety of [flavoenzymes](/source/Flavoenzyme) and their [coenzymes](/source/Coenzyme). Once formed, these anion free radicals reduce molecular oxygen to [superoxide](/source/Superoxide) and regenerate the unchanged parent compound. The net reaction is the oxidation of the flavoenzyme's coenzymes and the reduction of molecular oxygen to form superoxide. This catalytic behavior has been described as a [futile cycle](/source/Futile_cycle) or redox cycling. ## Redox reactions in geology [Blast furnaces](/source/Blast_furnace) of [Třinec Iron and Steel Works](/source/T%C5%99inec_Iron_and_Steel_Works), Czech Republic Minerals are generally oxidized derivatives of metals. [Iron](/source/Iron) is mined as ores such as [magnetite](/source/Magnetite) (Fe3O4) and [hematite](/source/Hematite) (Fe2O3). [Titanium](/source/Titanium) is mined as its dioxide, usually in the form of [rutile](/source/Rutile) (TiO2). These oxides must be reduced to obtain the corresponding metals, often achieved by heating these oxides with carbon or carbon monoxide as reducing agents. [Blast furnaces](/source/Blast_furnace) are the reactors where iron oxides and coke (a form of carbon) are combined to produce molten iron. The main chemical reaction producing the molten iron is:[28] - Fe2O3 + 3 CO → 2 Fe + 3 CO2 ## Redox reactions in soils [Electron transfer](/source/Electron_transfer) reactions are central to myriad processes and properties in soils, and [redox potential](/source/Redox_potential), quantified as Eh (platinum electrode potential ([voltage](/source/Voltage)) relative to the standard hydrogen electrode) or pe (analogous to pH as −log electron activity), is a master variable, along with pH, that controls and is governed by chemical reactions and biological processes. Early theoretical research with applications to flooded soils and [paddy rice](/source/Paddy_rice) production was seminal for subsequent work on thermodynamic aspects of redox and plant root growth in soils.[29] Later work built on this foundation, and expanded it for understanding redox reactions related to heavy metal oxidation state changes, [pedogenesis](/source/Pedogenesis) and morphology, organic compound degradation and formation, [free radical](/source/Free_radical) chemistry, [wetland](/source/Wetland) delineation, [soil remediation](/source/Soil_remediation), and various methodological approaches for characterizing the redox status of soils.[30][31] ## Mnemonics Main article: [List of chemistry mnemonics](/source/List_of_chemistry_mnemonics) The key terms involved in redox can be confusing.[32][33] For example, a reagent that is oxidized loses electrons; however, that reagent is referred to as the reducing agent. Likewise, a reagent that is reduced gains electrons and is referred to as the oxidizing agent.[34] These [mnemonics](/source/Mnemonics) are commonly used by students to help memorise the terminology:[35] - "[OIL RIG](/source/Oil_rig)" — **o**xidation **i**s **l**oss of electrons, **r**eduction **i**s **g**ain of electrons[32][33][34][35] - "LEO the lion says GER [grr]" — **l**oss of **e**lectrons is **o**xidation, **g**ain of **e**lectrons is **r**eduction[32][33][34][35] - "LEORA says GEROA" — the loss of electrons is called oxidation (reducing agent); the gain of electrons is called reduction (oxidizing agent).[34] - "RED CAT" and "AN OX", or "AnOx RedCat" ("an ox-red cat") — reduction occurs at the cathode and the anode is for oxidation - "RED CAT gains what AN OX loses" – reduction at the cathode gains (electrons) what anode oxidation loses (electrons) - "PANIC" – Positive Anode and Negative is Cathode. This applies to [electrolytic cells](/source/Electrolytic_cell) which release stored electricity, and can be recharged with electricity. PANIC does not apply to cells that can be recharged with redox materials. These [galvanic or voltaic cells](/source/Galvanic_cell), such as [fuel cells](/source/Fuel_cell), produce electricity from internal redox reactions. Here, the positive electrode is the cathode and the negative is the anode. ## See also - [Anaerobic respiration](/source/Anaerobic_respiration) - [Bessemer process](/source/Bessemer_process) - [Bioremediation](/source/Bioremediation) - [Calvin cycle](/source/Calvin_cycle) - [Chemical equation](/source/Chemical_equation) - [Chemical looping combustion](/source/Chemical_looping_combustion) - [Citric acid cycle](/source/Citric_acid_cycle) - [Electrochemical series](/source/Electrochemical_series) - [Electrochemistry](/source/Electrochemistry) - [Electrolysis](/source/Electrolysis) - [Electron equivalent](/source/Electron_equivalent) - [Electron transport chain](/source/Electron_transport_chain) - [Electrosynthesis](/source/Electrosynthesis) - [Galvanic cell](/source/Galvanic_cell) - [Hydrogenation](/source/Hydrogenation) - [Membrane potential](/source/Membrane_potential) - [Microbial fuel cell](/source/Microbial_fuel_cell) - [Murburn concept](/source/Murburn_concept) - [Nucleophilic abstraction](/source/Nucleophilic_abstraction) - [Organic redox reaction](/source/Organic_redox_reaction) - [Oxidative addition and reductive elimination](/source/Oxidative_addition) - [Oxidative phosphorylation](/source/Oxidative_phosphorylation) - [Partial oxidation](/source/Partial_oxidation) - [Pro-oxidant](/source/Pro-oxidant) - [Redox gradient](/source/Redox_gradient) - [Redox potential](/source/Redox_potential) - [Redox therapy](/source/Redox_therapy) - [Reducing agent](/source/Reducing_agent) - [Reducing atmosphere](/source/Reducing_atmosphere) - [Reduction potential](/source/Reduction_potential) - [Thermic reaction](/source/Exothermic) - [Transmetalation](/source/Transmetalation) - [Sulfur cycle](/source/Sulfur_cycle) ## References 1. **[^](#cite_ref-1)** ["Metals"](https://www.bbc.co.uk/bitesize/guides/zx2bh39/revision/5). *Bitesize*. BBC. [Archived](https://web.archive.org/web/20221103022135/https://www.bbc.co.uk/bitesize/guides/zx2bh39/revision/5) from the original on November 3, 2022. 1. **[^](#cite_ref-2)** ["redox – definition of redox in English | Oxford Dictionaries"](https://web.archive.org/web/20171001031248/https://en.oxforddictionaries.com/definition/redox). *Oxford Dictionaries | English*. Archived from [the original](https://en.oxforddictionaries.com/definition/redox) on October 1, 2017. Retrieved May 15, 2017. 1. ^ [***a***](#cite_ref-Petrucci2002_3-0) [***b***](#cite_ref-Petrucci2002_3-1) [***c***](#cite_ref-Petrucci2002_3-2) [***d***](#cite_ref-Petrucci2002_3-3) [***e***](#cite_ref-Petrucci2002_3-4) Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2002). *General Chemistry* (8th ed.). Prentice-Hall. [ISBN](/source/ISBN_(identifier)) [0-13-014329-4](https://en.wikipedia.org/wiki/Special:BookSources/0-13-014329-4). 1. **[^](#cite_ref-4)** ["Redox Reactions"](http://www.wiley.com/college/boyer/0470003790/reviews/redox/redox.htm). wiley.com. [Archived](https://web.archive.org/web/20120530081215/http://www.wiley.com/college/boyer/0470003790/reviews/redox/redox.htm) from the original on May 30, 2012. Retrieved May 9, 2012. 1. ^ [***a***](#cite_ref-gale_5-0) [***b***](#cite_ref-gale_5-1) [***c***](#cite_ref-gale_5-2) Haustein, Catherine Hinga (2014). ["Oxidation-reduction reaction"](https://link.gale.com/apps/doc/CV2644031629/SCIC?u=dc_demo&sid=SCIC&xid=baa9fde9). In K. Lee Lerner; Brenda Wilmoth Lerner (eds.). *The Gale Encyclopedia of Science* (5th ed.). Farmington Hills, MI: Gale Group. 1. **[^](#cite_ref-6)** Harper, Douglas. ["redox"](https://www.etymonline.com/word/redox). *[Online Etymology Dictionary](/source/Etymonline)*. 1. **[^](#cite_ref-i381_7-0)** Michaelis, L.; Flexner, Louis B. (1928). ["Oxidation-reduction systems of biological significance"](https://doi.org/10.1016%2FS0021-9258%2820%2979958-8). *Journal of Biological Chemistry*. **79** (2): 689–722. [doi](/source/Doi_(identifier)):[10.1016/S0021-9258(20)79958-8](https://doi.org/10.1016%2FS0021-9258%2820%2979958-8). 1. **[^](#cite_ref-8)** Pingarrón, José M.; Labuda, Ján; Barek, Jiří; Brett, Christopher M. A.; Camões, Maria Filomena; Fojta, Miroslav; Hibbert, D. Brynn (2020). ["Terminology of electrochemical methods of analysis (IUPAC Recommendations 2019)"](https://doi.org/10.1515%2Fpac-2018-0109). *Pure and Applied Chemistry*. **92** (4): 641–694. [doi](/source/Doi_(identifier)):[10.1515/pac-2018-0109](https://doi.org/10.1515%2Fpac-2018-0109). 1. ^ [***a***](#cite_ref-Petrucci2017_9-0) [***b***](#cite_ref-Petrucci2017_9-1) [***c***](#cite_ref-Petrucci2017_9-2) [***d***](#cite_ref-Petrucci2017_9-3) Petrucci, Ralph H.; Harwood, William S.; Herring, F. Geoffrey (2017). *General Chemistry: Principles and Modern applications* (11th ed.). Toronto: Pearson. [ISBN](/source/ISBN_(identifier)) [978-0-13-293128-1](https://en.wikipedia.org/wiki/Special:BookSources/978-0-13-293128-1). 1. **[^](#cite_ref-10)** ["Nitric Acid Fact Sheet"](https://essr.umd.edu/sites/default/files/2021-10/NitricAcidFactSheet.pdf) (PDF). *Department of Environmental Safety, Sustainability & Risk*. University of Maryland. Retrieved February 12, 2024. 1. ^ [***a***](#cite_ref-Whitten_11-0) [***b***](#cite_ref-Whitten_11-1) Whitten, Kenneth W.; Gailey, Kenneth D.; Davis, Raymond E. (1992). *General Chemistry* (4th ed.). Saunders College Publishin. p. 147. [ISBN](/source/ISBN_(identifier)) [0-03-072373-6](https://en.wikipedia.org/wiki/Special:BookSources/0-03-072373-6). 1. **[^](#cite_ref-12)** Jain JL (2004). *Fundamentals of Biochemistry*. S. Chand. [ISBN](/source/ISBN_(identifier)) [81-219-2453-7](https://en.wikipedia.org/wiki/Special:BookSources/81-219-2453-7). 1. **[^](#cite_ref-Lehninger-2017_13-0)** Lehninger AL, Nelson DL, Cox MM (January 1, 2017). *Lehninger Principles of Biochemistry* (Seventh ed.). New York, NY. [ISBN](/source/ISBN_(identifier)) [9781464126116](https://en.wikipedia.org/wiki/Special:BookSources/9781464126116). [OCLC](/source/OCLC_(identifier)) [986827885](https://search.worldcat.org/oclc/986827885).{{[cite book](https://en.wikipedia.org/wiki/Template:Cite_book)}}: CS1 maint: location missing publisher ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_location_missing_publisher)) 1. **[^](#cite_ref-14)** ["Oxidizing and Reducing Agents"](https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch19/oxred_3.php#top). 1. **[^](#cite_ref-15)** Hudlický, Miloš (1996). *Reductions in Organic Chemistry*. Washington, D.C.: American Chemical Society. p. 429. [ISBN](/source/ISBN_(identifier)) [978-0-8412-3344-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-8412-3344-7). 1. **[^](#cite_ref-16)** Hudlický, Miloš (1990). [*Oxidations in Organic Chemistry*](https://archive.org/details/oxidationsinorga00hudl/page/456). Washington, D.C.: American Chemical Society. pp. [456](https://archive.org/details/oxidationsinorga00hudl/page/456). [ISBN](/source/ISBN_(identifier)) [978-0-8412-1780-5](https://en.wikipedia.org/wiki/Special:BookSources/978-0-8412-1780-5). 1. **[^](#cite_ref-17)** Bockris, John O'M.; Reddy, Amulya K. N. (1970). *Modern Electrochemistry*. Plenum Press. pp. 352–3. 1. **[^](#cite_ref-18)** Bockris, John O'M.; Reddy, Amulya K.N. (2013) [1970]. [*Modern Electrochemistry*](https://books.google.com/books?id=0xzlBwAAQBAJ&pg=PA494). Vol. 1. Springer Science & Business Media. p. 494. [ISBN](/source/ISBN_(identifier)) [9781461574675](https://en.wikipedia.org/wiki/Special:BookSources/9781461574675). Retrieved March 29, 2020. The homogeneous proton-transfer reactions described are similar to homogeneous electron-transfer reactions in that the overall electron-transfer reaction can be decomposed into one electronation reaction and one deelectronation reaction. 1. **[^](#cite_ref-19)** IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. [ISBN](/source/ISBN_(identifier)) [0-9678550-9-8](https://en.wikipedia.org/wiki/Special:BookSources/0-9678550-9-8). [https://goldbook.iupac.org/terms/view/R05222](https://goldbook.iupac.org/terms/view/R05222) 1. **[^](#cite_ref-20)** IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. [ISBN](/source/ISBN_(identifier)) [0-9678550-9-8](https://en.wikipedia.org/wiki/Special:BookSources/0-9678550-9-8). [https://goldbook.iupac.org/terms/view/O04362](https://goldbook.iupac.org/terms/view/O04362) 1. **[^](#cite_ref-21)** Mailloux, Ryan J. (April 2015). ["Teaching the fundamentals of electron transfer reactions in mitochondria and the production and detection of reactive oxygen species"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4348434). *Redox Biology*. **4**: 381–398. [doi](/source/Doi_(identifier)):[10.1016/j.redox.2015.02.001](https://doi.org/10.1016%2Fj.redox.2015.02.001). [PMC](/source/PMC_(identifier)) [4348434](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4348434). [PMID](/source/PMID_(identifier)) [25744690](https://pubmed.ncbi.nlm.nih.gov/25744690). 1. **[^](#cite_ref-22)** [IUPAC](/source/International_Union_of_Pure_and_Applied_Chemistry), *[Compendium of Chemical Terminology](/source/IUPAC_books#Gold_Book)*, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "[Inner-sphere electron transfer](https://goldbook.iupac.org/terms/view/I03052.html)". [doi](/source/Doi_(identifier)):[10.1351/goldbook.I03052](https://doi.org/10.1351%2Fgoldbook.I03052) 1. **[^](#cite_ref-23)** [IUPAC](/source/International_Union_of_Pure_and_Applied_Chemistry), *[Compendium of Chemical Terminology](/source/IUPAC_books#Gold_Book)*, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "[Outer-sphere electron transfer](https://goldbook.iupac.org/terms/view/O04351.html)". [doi](/source/Doi_(identifier)):[10.1351/goldbook.O04351](https://doi.org/10.1351%2Fgoldbook.O04351) 1. **[^](#cite_ref-24)** ["Bond Energy and Enthalpy"](https://uen.pressbooks.pub/introductorychemistry/chapter/bond-energy-and-enthalpy/). 1. **[^](#cite_ref-25)** Brown, Theodore L., ed. (2015). *Chemistry: the central science* (13 ed.). Boston, Mass.: Pearson. pp. Chapter 4. [ISBN](/source/ISBN_(identifier)) [978-0-321-91041-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-321-91041-7). 1. **[^](#cite_ref-26)** ["15.11: Bond Enthalpies and Exothermic or Endothermic Reactions"](https://chem.libretexts.org/Bookshelves/General_Chemistry/ChemPRIME_(Moore_et_al.)/15%3A_Thermodynamics-_Atoms_Molecules_and_Energy/15.11%3A_Bond_Enthalpies_and_Exothermic_or_Endothermic_Reactions). *Chemistry LibreTexts*. May 9, 2016. Retrieved November 15, 2025. 1. **[^](#cite_ref-27)** ["Titles of Volumes 1–44 in the Metal Ions in Biological Systems Series"](https://www.degruyter.com/document/doi/10.1515/9783110589771-005). *Metals, Microbes, and Minerals - the Biogeochemical Side of Life*. De Gruyter. 2021. pp. xxiii–xxiv. [doi](/source/Doi_(identifier)):[10.1515/9783110589771-005](https://doi.org/10.1515%2F9783110589771-005). [ISBN](/source/ISBN_(identifier)) [9783110588903](https://en.wikipedia.org/wiki/Special:BookSources/9783110588903). [S2CID](/source/S2CID_(identifier)) [242013948](https://api.semanticscholar.org/CorpusID:242013948). 1. **[^](#cite_ref-28)** Oeters, Franz; Ottow, Manfred; Meiler, Heinrich; Lüngen, Hans Bodo; Koltermann, Manfred; Buhr, Andreas; Yagi, Jun-Ichiro; Formanek, Lothar; Rose, Fritz; Flickenschild, Jürgen; Hauk, Rolf; Steffen, Rolf; Skroch, Reiner; Mayer-Schwinning, Gernot; Bünnagel, Heinz-Lothar; Hoff, Hans-Georg (2006). "Iron". *[Ullmann's Encyclopedia of Industrial Chemistry](/source/Ullmann's_Encyclopedia_of_Industrial_Chemistry)*. Weinheim: Wiley-VCH. [doi](/source/Doi_(identifier)):[10.1002/14356007.a14_461.pub2](https://doi.org/10.1002%2F14356007.a14_461.pub2). [ISBN](/source/ISBN_(identifier)) [978-3-527-30673-2](https://en.wikipedia.org/wiki/Special:BookSources/978-3-527-30673-2). 1. **[^](#cite_ref-29)** Ponnamperuma, F.N. (1972). *The Chemistry of Submerged Soils*. Advances in Agronomy. Vol. 24. pp. 29–96. [doi](/source/Doi_(identifier)):[10.1016/S0065-2113(08)60633-1](https://doi.org/10.1016%2FS0065-2113%2808%2960633-1). [ISBN](/source/ISBN_(identifier)) [978-0-12-000724-0](https://en.wikipedia.org/wiki/Special:BookSources/978-0-12-000724-0). 1. **[^](#cite_ref-30)** Bartlett, Richmond J.; James, Bruce R. (1991). "Redox chemistry of soils". *Advances in Agronomy*. **39**: 151–208. 1. **[^](#cite_ref-31)** James, Bruce R.; Brose, Dominic A. (2012). "Oxidation-reduction phenomena". In Huang, Pan Ming; Li, Yuncong; Sumner, Malcolm E. (eds.). *Handbook of soil sciences: properties and processes* (second ed.). Boca Raton, Florida: [CRC Press](/source/CRC_Press). pp. 14-1 -- 14-24. [ISBN](/source/ISBN_(identifier)) [978-1-4398-0305-9](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4398-0305-9). 1. ^ [***a***](#cite_ref-Robertson_32-0) [***b***](#cite_ref-Robertson_32-1) [***c***](#cite_ref-Robertson_32-2) Robertson, William (2010). [*More Chemistry Basics*](https://books.google.com/books?id=hIzuarlXtH4C&pg=PA82). National Science Teachers Association. p. 82. [ISBN](/source/ISBN_(identifier)) [978-1-936137-74-9](https://en.wikipedia.org/wiki/Special:BookSources/978-1-936137-74-9). 1. ^ [***a***](#cite_ref-Chemistry_ConceptsAndApplications_33-0) [***b***](#cite_ref-Chemistry_ConceptsAndApplications_33-1) [***c***](#cite_ref-Chemistry_ConceptsAndApplications_33-2) Phillips, John; Strozak, Victor; Wistrom, Cheryl (2000). *Chemistry: Concepts and Applications*. Glencoe McGraw-Hill. p. 558. [ISBN](/source/ISBN_(identifier)) [978-0-02-828210-7](https://en.wikipedia.org/wiki/Special:BookSources/978-0-02-828210-7). 1. ^ [***a***](#cite_ref-Rodgers_34-0) [***b***](#cite_ref-Rodgers_34-1) [***c***](#cite_ref-Rodgers_34-2) [***d***](#cite_ref-Rodgers_34-3) Rodgers, Glen (2012). [*Descriptive Inorganic, Coordination, and Solid-State Chemistry*](https://books.google.com/books?id=g_ybia0hGw8C&pg=PA330). Brooks/Cole, Cengage Learning. p. 330. [ISBN](/source/ISBN_(identifier)) [978-0-8400-6846-0](https://en.wikipedia.org/wiki/Special:BookSources/978-0-8400-6846-0). 1. ^ [***a***](#cite_ref-Zumhahl_35-0) [***b***](#cite_ref-Zumhahl_35-1) [***c***](#cite_ref-Zumhahl_35-2) Zumdahl, Steven; Zumdahl, Susan (2009). [*Chemistry*](https://books.google.com/books?id=IdhYqXy37KIC&pg=PA160). Houghton Mifflin. p. 160. [ISBN](/source/ISBN_(identifier)) [978-0-547-05405-6](https://en.wikipedia.org/wiki/Special:BookSources/978-0-547-05405-6). ## Further reading - Schüring, J.; Schulz, H. D.; Fischer, W. R.; Böttcher, J.; Duijnisveld, W. H., eds. (1999). *Redox: Fundamentals, Processes and Applications*. Heidelberg: Springer-Verlag. p. 246. [hdl](/source/Hdl_(identifier)):[10013/epic.31694.d001](https://hdl.handle.net/10013%2Fepic.31694.d001). [ISBN](/source/ISBN_(identifier)) [978-3-540-66528-1](https://en.wikipedia.org/wiki/Special:BookSources/978-3-540-66528-1). - Tratnyek, Paul G.; Grundl, Timothy J.; Haderlein, Stefan B., eds. (2011). *Aquatic Redox Chemistry*. ACS Symposium Series. Vol. 1071. [doi](/source/Doi_(identifier)):[10.1021/bk-2011-1071](https://doi.org/10.1021%2Fbk-2011-1071). [ISBN](/source/ISBN_(identifier)) [978-0-8412-2652-4](https://en.wikipedia.org/wiki/Special:BookSources/978-0-8412-2652-4). ## External links Wikiquote has quotations related to ***[Redox](https://en.wikiquote.org/wiki/Special:Search/Redox)***. Wikimedia Commons has media related to [Redox reactions](https://commons.wikimedia.org/wiki/Category:Redox_reactions). v t e Basic reaction mechanisms Nucleophilic substitutions Unimolecular nucleophilic substitution (SN1) Bimolecular nucleophilic substitution (SN2) Nucleophilic internal substitution (SNi) Nucleophilic acyl substitution (SNAcyl) Electrophilic substitutions Electrophilic aromatic substitution (SEAr) Elimination reactions E1cB-elimination Ei elimination Addition reactions Electrophilic addition (AE) Nucleophilic addition (AN) Free-radical addition Cycloaddition Oxidative addition Unimolecular reactions Intramolecular reaction Isomerization Photodissociation Lindemann mechanism RRKM theory Electron/Proton transfer reactions Redox Harpoon reaction Grotthuss mechanism Marcus theory Inner sphere electron transfer Outer sphere electron transfer Medium effects Solvent effects Cage effect Matrix isolation Related topics Elementary reaction Reaction dynamics Reactive intermediate Radical (chemistry) Molecularity Stereochemistry Catalysis Collision theory Arrow pushing Potential energy surface More O'Ferrall–Jencks plot Chemical kinetics Rate equation Equilibrium constant Rate-determining step Reaction coordinate Energy profile (chemistry) Transition state theory Activation energy Activated complex Arrhenius equation Eyring equation Michaelis–Menten kinetics Diffusion-controlled reaction Authority control databases International GND National United States France BnF data Japan Czech Republic Israel Other Yale LUX --- Adapted from the Wikipedia article [Redox](https://en.wikipedia.org/wiki/Redox) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Redox?action=history)). 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