Oxidizing agent

Encyclopedia : O : OX : OXI : Oxidizing agent

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An oxidizing agent (also called an oxidizer or oxidant) is referred to

1. A chemical compound that readily gives up oxygen or
2. A substance that gains electrons in a redox chemical reaction.

In doing so, the oxidizing agent becomes reduced in the process.

In simple terms:

• The oxidizing agent is reduced.
• The reducing agent is oxidized.
• All parts of an element in a redox reaction have an oxidation number.
• Redox reactions occur when electrons are exchanged.

Example of oxidation

The formation of iron(III) oxide;

4Fe + 3O₂ → 2Fe₂O₃

In the above equation the Iron III (Fe) has an oxidation number of 0 and in the end the oxidation number has increased to 3+. For oxygen (O) the oxidation number began as 0 and has decreased to 2−. These changes can be viewed as two "half-reactions" that occur concurrently:

1. Oxidation Half Reaction: Fe⁰ → Fe³⁺ + 3e⁻
2. Reduction Half Reaction: O₂ + 4e⁻ → 2 O²⁻

Iron III (Fe) has been oxidized because the oxidation number increased and is the reducing agent because it gave electrons to the oxygen (O). oxygen (O) has been reduced because the oxidation number has decreased and is the oxidizing agent because it took electrons from iron (Fe)

Alternate meanings

Because the process of oxidation is so widespread (explosives, chemical synthesis, corrosion), the term oxidizing agent has acquired multiple meanings.

One definition, an oxidizing agent receives - or accepts - electrons from a reagent. In this context, the oxidizing agent is called an electron acceptor. A classic oxidizing agent is the ferrocenium ion [Fe(C₅H₅)₂]⁺ which accepts an electron to form Fe(C₅H₅)₂. Of great interest to chemists are the details of the electron transfer event, which can be described as inner sphere or outer sphere.

In another more colloquial usage, an oxidizing agent transfers oxygen atoms to the substrate. In this context, the oxidizing agent can be called an oxygenation reagent or oxygen-atom transfer agent. Examples include [MnO₄]⁻ permanganate, [CrO₄]²⁻ chromate, and OsO₄ osmium tetroxide. Notice that these species are all oxides, and in fact, polyoxides. In some cases, these oxides can also serve as electron acceptors, as illustrated by the conversion of [MnO₄]⁻ to [MnO₄]²⁻, manganate.

Common oxidizing agents

• Hypochlorite and other hypohalite compounds such as Bleach
• Iodine and other halogens
• Chlorite, chlorate, perchlorate, and other analogous halogen compounds
• Permanganate salts
• Ammonium cerium(IV) nitrate and probably related Cerium(IV) compounds
• Hexavalent chromium compounds such as chromic and dichromic acids and chromium trioxide, Pyridinium chlorochromate (PCC), and chromate/dichromate compounds
• Peroxide compounds
• Tollen's Reagent
• sulfoxides
• Persulfuric acid
• Ozone
• Osmium tetroxide ([OsO₄)
• Nitric acid

Common oxidizing agents and their products

Agent	Product(s)
O2 oxygen	Various including oxides, H2O, or CO2
O3 ozone	Various including ketones and aldehydes, H2O, see ozonolysis
F2 fluorine	F−
Cl2 chlorine	Cl−
Br2 bromine	Br−
I2 iodine	I−, I3−
ClO− hypochlorite	Cl−, H2O
ClO3− chlorate	Cl−, H2O
HNO3 nitric acid	NO nitric oxide NO2 nitrogen dioxide
Hexavalent chromium CrO3 chromium(VI) oxide CrO42− chromate Cr2O72− dichromate	Cr3+, H2O
MnO4− permanganate MnO42− manganate	Mn2+ (acidic) or MnO2 (basic)
H2O2, other peroxides	Various including oxides, H2O

There are many other oxidizing agents; too numerous to list here.

See also

• Reducing agent
• Organic oxidation

 

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