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oxidant

  (ŏk'sĭ-dənt) pronunciation
n.

A substance that oxidizes another substance; an oxidizing agent.

[French oxidant, present participle of oxider, to oxidize, from oxide, oxide. See oxide.]


 
 
Sci-Tech Encyclopedia: Oxidizing agent

A participant in a chemical reaction that absorbs electrons from another reactant. In the process a component atom of this substance undergoes a decrease in oxidation number. In this action as an oxidizing agent, the substance undergoes reduction.

A measure of the effectiveness of a reagent as an oxidizing agent is its reduction potential. This is, in electrochemical terms, the equivalent of the free-energy change for the reduction process. The element with the highest reduction potential (and, therefore, the strongest oxidizing agent) is fluorine, F2. The practical effectiveness of a given oxidizing (or reducing) agent will depend upon both the thermodynamics and the available kinetic pathway for the reaction process. See also Chemical thermodynamics.

Substances that are widely used as oxidizing agents in chemistry include ozone (O3), permanganate ion (MnO4), nitric acid (HNO3), as well as oxygen itself. Organic chemists have empirically developed combinations of reagents to carry out specific oxidation steps in synthetic processes. The action of molecular oxygen as an oxidizing agent may be made more specific by photochemical excitation to an excited singlet electronic state.


 
Dental Dictionary: oxidizing agent

n

An agent that provides oxygen in reaction with another substance or, in the broader and more definitive chemical sense, a chemical capable of accepting electrons and thereby decreasing the negative charge on an atom of the substance being oxidized.

 

The electron acceptor in an oxidation–reduction (redox) reaction.

 
Wikipedia: oxidizing agent
European Union Chemical hazard symbol for oxidizing agents
Dangerous goods label for oxidizing agents
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Dangerous goods label for oxidizing agents
Oxidizing agent placard
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Oxidizing agent placard

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

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

The former definition is not applicable to what most people read about. It is also the sense that most organic chemists use the term. In both cases, the oxidizing agent becomes reduced in the process.

In simple terms:

  • The oxidizing agent is reduced.
  • The reducing agent is oxidized.
  • All atoms in a molecule can be assigned an oxidation number. This number changes when an oxidant acts on a substrate.
  • Redox reactions occur when electrons are exchanged.

A mnemonic for differentiating the reactions is "OIL RIG": Oxidation Is Loss, Reduction Is Gain (of electrons) or "LEO the lion says GER" (Lose Electrons: Oxidation, Gain Electrons: Reduction)

Example of oxidation

The formation of iron(III) oxide;

4Fe + 3O2 → 2Fe2O3

In the above equation, the Iron (Fe) has an oxidation number of 0 before and 3+ after the reaction. For oxygen (O) the oxidation number began as 0 and 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, OsO4 osmium tetroxide, and especially ClO4 perchlorate. 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.

The strict dangerous goods definition of an oxidizing agent are substances that, while in themselves not necessarily combustible, may, generally by yielding oxygen, cause, or contribute to, the combustion of other material. (Australian Dangerous Goods Code 6th Edition) By this definition some materials that are classified as oxidizing agents by analytical chemists are not classified as oxidizing agents in a dangerous goods sense. An example is potassium dichromate which does not pass the dangerous goods test of an oxidizing agent.

Common oxidizing agents

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 trioxide
CrO42− chromate
Cr2O72− dichromate
Cr3+, H2O
MnO4 permanganate
MnO42− manganate
Mn2+ (acidic) or MnO2 (basic)
H2O2, other peroxides Various including oxides, H2O

See also


 
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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved.  Read more
Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Oxidizing agent" Read more

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