Oxidizing agent
From Wikipedia, the free encyclopedia
An oxidizing agent (also called an oxidizer or oxidant) is referred to as
- A chemical compound that readily transfers oxygen atoms or
- A substance that gains electrons in a redox chemical reaction.
The former definition is more 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)
[edit] 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:
- Oxidation Half Reaction: Fe0 → Fe3+ + 3e−
- 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)
[edit] 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.
[edit] 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
[edit] 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.
[edit] See also
es:Oxidante fr:Comburant lt:Oksidatorius nl:Oxidator pl:Utleniacz ru:Окислитель zh:氧化剂
