In chemistry, an oxidizing agent (oxidant, oxidizer) is a substance that has the ability
to oxidize other substances — in other words to accept their electrons. Common oxidizing
agents are oxygen, hydrogen peroxide and the halogens.
In one sense, an oxidizing agent is a chemical species that undergoes a chemical
reaction that takes one or more electrons from another atom. 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.
Contents
Electron acceptorsEdit
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 Fe(C
5H
5)+
2, which accepts an electron to form Fe(C5H5)2. One of the strongest acceptors commercially
available is "Magic blue", the radical cation derived from N(C6H4-4-Br)3.[1]
Extensive tabulations of ranking the electron accepting properties of various reagents
(redox potentials) are available, see Standard electrode potential (data page).
Atom-transfer reagentsEdit
In more common usage, an oxidising agent transfers oxygen atoms to a substrate. In this
context, the oxidising agent can be called an oxygenation reagent or oxygen-atom transfer
(OAT) agent.[2] Examples include MnO−
4 (permanganate), CrO2−
4 (chromate), OsO4 (osmium tetroxide), and especially ClO−
4 (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 MnO−
4 to MnO2−
4, manganate.
Common oxidizing agentsEdit
Oxygen (O2)
Ozone (O3)
Hydrogen peroxide (H2O2) and other inorganic peroxides, Fenton's reagent
Fluorine (F2), chlorine (Cl2), and other halogens
Nitric acid (HNO3) and nitrate compounds
Sulfuric acid (H2SO4)
Peroxydisulfuric acid (H2S2O8)
Peroxymonosulfuric acid (H2SO5)
Chlorite, chlorate, perchlorate, and other analogous halogen compounds
Hypochlorite and other hypohalite compounds, including household bleach (NaClO)
Hexavalent chromium compounds such as chromic and dichromic acids and chromium
trioxide, pyridinium chlorochromate (PCC), and chromate/dichromate compounds
Permanganate compounds such as potassium permanganate
Sodium perborate
Nitrous oxide (N2O), Nitrogen dioxide/Dinitrogen tetroxide (NO2 / N2O4)
Potassium nitrate (KNO3), the oxidizer in black powder
Sodium bismuthate
Cerium (IV) compounds such as ceric ammonium nitrate and ceric sulfate
Dangerous materials definitionEdit
The dangerous materials definition of an oxidizing agent is a substance that can cause or
contribute to the combustion of other material.[3] 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."[4]
