Oxygen compounds
The oxidation state of oxygen is −2 in almost all known compounds of oxygen. The oxidation state −1 is found in a few compounds such as peroxides. Compounds containing oxygen in other oxidation states are very uncommon: −1⁄2 (superoxides), −1⁄3 (ozonides), 0 (elemental, hypofluorous acid), +1⁄2 (dioxygenyl), +1 (dioxygen difluoride), and +2 (oxygen difluoride).
Oxygen is reactive and will form oxides with all other elements except the noble gases helium, neon, argon and krypton.[1]
Oxides
2O
3, form when oxygen combines with other elements
Due to its
2O
3) must be formed by an indirect route.
The
Oxygen is present as compounds in the atmosphere in trace quantities in the form of
.Other inorganic compounds
2)
The rest of the Earth's crust is formed also of oxygen compounds, most importantly calcium carbonate (in limestone) and silicates (in feldspars). Water-soluble silicates in the form of Na
4SiO
4, Na
2SiO
3, and Na
2Si
2O
5 are used as detergents and adhesives.[6]
Peroxides retain some of oxygen's original molecular structure ((−O-O−). White or light yellow sodium peroxide (Na
2O
2) is formed when metallic sodium is burned in oxygen. Each oxygen atom in its peroxide ion may have a full octet of 4 pairs of electrons.[6] Superoxides are a class of compounds that are very similar to peroxides, but with just one unpaired electron for each pair of oxygen atoms (O−
2).[6] These compounds form by oxidation of alkali metals with larger ionic radii (K, Rb, Cs). For example, potassium superoxide (KO
2) is an orange-yellow solid formed when potassium reacts with oxygen.
Hydrogen peroxide (H
2O
2) can be produced by passing a volume of 96% to 98% hydrogen and 2 to 4% oxygen through an electric discharge.[7] A more commercially-viable method is to allow autoxidation of an organic intermediate, 2-ethylanthrahydroquinone dissolved in an organic solvent, to oxidize to H
2O
2 and 2-ethylanthraquinone.[7] The 2-ethylanthraquinone is then reduced and recycled back into the process.
When dissolved in water, many metallic oxide form
Oxygenated
3PW
12O
40) and octadecamolybdophosphoric acid (H
6P
2Mo
18O
62).
Oxygen can form oxides with heavier noble gases xenon and radon, although this needs indirect methods. Even though no oxides of krypton are known, oxygen is able to form covalent bonds with krypton in an unstable compound Kr(OTeF5)2.
One unexpected oxygen compound is dioxygenyl hexafluoroplatinate, O+
2PtF−
6, discovered in studying the properties of platinum hexafluoride (PtF
6).[8] A change in color when this compound was exposed to atmospheric air suggested that dioxygen was being oxidized (in turn the difficulty of oxidizing oxygen led to the hypothesis that xenon might be oxidized by PtF
6, resulting in discovery of the first xenon compound xenon hexafluoroplatinate Xe+
PtF−
6). The cations of oxygen are formed only in the presence of stronger oxidants than oxygen, which limits them to the action of fluorine and certain fluorine compounds. Simple oxygen fluorides are known.[9]
Organic compounds
(oxygen is in red, carbon in black and hydrogen in white)
Among the most important classes of organic compounds that contain oxygen are (where "R" is an organic group):
3)
2CO) and phenol (C
6H
5OH) are used as feeder materials in the synthesis of many different substances. Other important organic compounds that contain oxygen are: glycerol, formaldehyde, glutaraldehyde, citric acid, acetic anhydride, acetamide, etc. Epoxides are ethers
Oxygen reacts spontaneously with many organic compounds at or below room temperature in a process called autoxidation.[7] Alkaline solutions of pyrogallol, benzene-1,2,3-triol absorb oxygen from the air, and are used in the determination of the atmospheric concentration of oxygen. Most of the organic compounds that contain oxygen are not made by direct action of oxygen. Organic compounds important in industry and commerce are made by direct oxidation of a precursor include:[6]
- Ethylene oxide (used to make the antifreeze ethylene glycol) is obtained by direct oxidation of ethylene:
- C
2H
4 + ½ O
2 +catalyst
———→ C
2H
4O
- C
- Peracetic acid (feeder material for various epoxy compounds) is obtained from acetaldehyde:
- CH
3CHO + O
2 + catalyst
———→ CH
3C(O)-OOH
- CH
Biomolecules
The element is found in almost all
See also
References
- ^ Chemical properties of Oxygen[1], Lenntech. Accessed January 25, 2008. "Oxygen is reactive and will form oxides with all other elements except helium, neon, argon and krypton."
- ^ P. Maksyutenko, T. R. Rizzo, and O. V. Boyarkin (2006). "A direct measurement of the dissociation energy of water", J. Chem. Phys. 125 doi 181101.
- ^ Chaplin, Martin (2008-01-04). "Water Hydrogen Bonding". Retrieved 2008-01-06.
- ^ Also, since oxygen has a higher electronegativity than
hydrogen, the charge difference makes it a polar molecule. The interactions between the different dipolesof each molecule cause a net attraction force.
- ^ The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodizing.
- ^ a b c d Cook 1968, p.507
- ^ a b c d Cook 1968, p.506
- ^ Cook 1968, p.505
- ^ Cotton, F. Albert and Wilkinson, Geoffrey (1972). Advanced Inorganic Chemistry: A comprehensive Text. (3rd Edition). New York, London, Sydney,
Toronto: Interscience Publications. ISBN 0-471-17560-9.
- Cook, Gerhard A.; Lauer, Carol M. (1968). "Oxygen". In Clifford A. Hampel (ed.). The Encyclopedia of the Chemical Elements. New York: Reinhold Book Corporation. pp. 499–512. LCCN 68-29938.