An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or
electron acceptor) is a substance in a
redox
Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...
chemical reaction that gains or "
accepts"/"receives" an
electron
The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family,
and are generally thought to be elementary particles because they have n ...
from a (called the , , or ). In other words, an oxidizer is any substance that
oxidizes another substance. The
oxidation state, which describes the degree of loss of
electrons, of the oxidizer decreases while that of the reductant increases; this is expressed by saying that oxidizers "undergo reduction" and "are reduced" while reducers "undergo oxidation" and "are oxidized".
Common oxidizing agents are
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
,
hydrogen peroxide and the
halogens.
In one sense, an oxidizing agent is a chemical species that undergoes a
chemical reaction in which it gains one or more electrons. In that sense, it is one component in an
oxidation–reduction (redox) reaction. In the second sense, an oxidizing agent is a chemical species that transfers electronegative atoms, usually oxygen, to a substrate.
Combustion, many explosives, and
organic redox reactions involve atom-transfer reactions.
Electron acceptors
100px, is an organic electron-acceptor.">Tetracyanoquinodimethane is an organic electron-acceptor.
Electron acceptors participate in
electron-transfer reactions. In this context, the oxidizing agent is called an electron acceptor and the reducing agent is called an electron donor. A classic oxidizing agent is the
ferrocenium ion , which accepts an electron to form Fe(C
5H
5)
2. One of the strongest acceptors commercially available is "
Magic blue", the radical cation derived from N(C
6H
4-4-Br)
3.
Extensive tabulations of ranking the electron accepting properties of various reagents (redox potentials) are available, see
Standard electrode potential (data page).
Atom-transfer reagents
In more common usage, an oxidizing agent transfers oxygen atoms to a substrate. In this context, the oxidizing agent can be called an oxygenation reagent or oxygen-atom transfer (OAT) agent. Examples include (
permanganate
A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a ...
), (
chromate), OsO
4 (
osmium tetroxide), and especially (
perchlorate). Notice that these species are all
oxides.
In some cases, these oxides can also serve as electron acceptors, as illustrated by the conversion of to ,
manganate.
Common oxidizing agents
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Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
(O
2)
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Ozone (O
3)
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Hydrogen peroxide (H
2O
2) and other inorganic
peroxides,
Fenton's reagent
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Fluorine (F
2),
chlorine (Cl
2), and other
halogens
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Nitric acid (HNO
3) and
nitrate compounds such as
potassium nitrate
Potassium nitrate is a chemical compound with the chemical formula . This alkali metal nitrate salt is also known as Indian saltpetre (large deposits of which were historically mined in India). It is an ionic salt of potassium ions K+ and ...
(KNO
3), the oxidizer in
black powder
*
Potassium chlorate (KClO
3)
*
Sulfuric acid (H
2SO
4)
*
Peroxydisulfuric acid (H
2S
2O
8)
*
Peroxymonosulfuric acid (H
2SO
5)
*
Hypochlorite,
chlorite,
chlorate,
perchlorate, and other analogous
halogen compounds like household bleach (NaClO)
*Hexavalent
chromium compounds such as
chromic and dichromic acids and chromium trioxide,
pyridinium chlorochromate (PCC), and
chromate/dichromate compounds such as
Sodium dichromate
Sodium dichromate is the inorganic compound with the formula Na2 Cr2 O7. However, the salt is usually handled as its dihydrate Na2Cr2O7·2 H2O. Virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compound ...
(Na
2Cr
2O
7)
*
Permanganate
A permanganate () is a chemical compound containing the manganate(VII) ion, , the conjugate base of permanganic acid. Because the manganese atom is in the +7 oxidation state, the permanganate(VII) ion is a strong oxidizing agent. The ion is a ...
compounds such as
potassium permanganate (KMnO
4)
*
Sodium perborate (·)
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Nitrous oxide (N
2O),
Nitrogen dioxide/
Dinitrogen tetroxide (NO
2 / N
2O
4)
*
Sodium bismuthate (NaBiO
3)
*Cerium (IV) compounds such as
ceric ammonium nitrate and
ceric sulfate
*
Lead dioxide (PbO
2)
Dangerous materials definition
The
dangerous goods definition of an oxidizing agent is a substance that can cause or contribute to the combustion of other material. By this definition some materials that are classified as oxidizing agents by analytical chemists are not classified as oxidizing agents in a dangerous materials sense. An example is
potassium dichromate, which does not pass the dangerous goods test of an oxidizing agent.
The
U.S. Department of Transportation defines oxidizing agents specifically. There are two definitions for oxidizing agents governed under DOT regulations. These two are
Class 5; Division 5.1(a)1 and Class 5; Division 5.1(a)2. Division 5.1 "means a material that may, generally by yielding oxygen, cause or enhance the combustion of other materials." Division 5.(a)1 of the DOT code applies to solid oxidizers "if, when tested in accordance with the UN Manual of Tests and Criteria (IBR, see § 171.7 of this subchapter), its mean burning time is less than or equal to the burning time of a 3:7 potassium bromate/cellulose mixture." 5.1(a)2 of the DOT code applies to liquid oxidizers "if, when tested in accordance with the UN Manual of Tests and Criteria, it spontaneously ignites or its mean time for a pressure rise from 690 kPa to 2070 kPa gauge is less than the time of a 1:1 nitric acid (65 percent)/cellulose mixture."
[49 CFR 172.127 General Requirements for Shipments and Packagings; Subpart D]
Common oxidizing agents and their products
See also
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References
{{Authority control
Chemical properties
Electrochemistry
Redox