Anoxidizing agent (also known as anoxidant,oxidizer,electron recipient, orelectron acceptor) is a substance in aredox chemical reaction that gains or "accepts"/"receives" anelectron from areducing agent (called thereductant,reducer, orelectron donor). In other words, an oxidizer is any substance thatoxidizes another substance. Theoxidation state, which describes the degree of loss ofelectrons, 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 areoxygen,hydrogen peroxide, and thehalogens.
In one sense, an oxidizing agent is a chemical species that undergoes achemical reaction in which it gains one or more electrons. In that sense, it is one component in anoxidation–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, andorganic redox reactions involve atom-transfer reactions.
Electron acceptors participate inelectron-transfer reactions. In this context, the oxidizing agent is called anelectron acceptor and the reducing agent is called anelectron donor. A classic oxidizing agent is theferrocenium ionFe(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.[2]
Extensive tabulations of ranking the electron accepting properties of various reagents (redox potentials) are available, seeStandard electrode potential (data page).
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.[3] Examples includeMnO− 4 (permanganate),CrO2− 4 (chromate), OsO4 (osmium tetroxide), and especiallyClO− 4 (perchlorate). Notice that these species are alloxides.
In some cases, these oxides can also serve as electron acceptors, as illustrated by the conversion ofMnO− 4 toMnO2− 4,iepermanganate tomanganate.
Thedangerous goods definition of an oxidizing agent is a substance that can cause or contribute to the combustion of other material.[4] 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 ispotassium dichromate, which does not pass the dangerous goods test of an oxidizing agent.
TheU.S. Department of Transportation defines oxidizing agents specifically. There are two definitions for oxidizing agents governed under DOT regulations. These two areClass 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."[5]
