Lewis electron configuration of superoxide. The six outer shell electrons of each oxygen atom are shown in black; one electron pair is shared (middle); the unpaired electron is shown in the upper left and the additional electron conferring a negative charge is shown in red.

Superoxide is the anion O₂⁻.^[1] With one unpaired electron, the superoxide ion is a free radical and therefore paramagnetic. Image File history File links Superoxide. ... Image File history File links Superoxide. ... G. N. Lewis Lewis structures, also called electron-dot structures or electron-dot diagrams, are diagrams that show the bonding between atoms of a molecule, and the lone pairs of electrons that may exist in the molecule. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... An anion is an ion with negative charge. ... The electron is a fundamental subatomic particle that carries a negative electric charge. ... Multivalent redirects here. ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... Paramagnetism is the tendency of the atomic magnetic dipoles, due to quantum-mechanical spin, in a material that is otherwise non-magnetic to align with an external magnetic field. ...

Synthesis, basic reactions, and structure

The salts CsO₂, RbO₂, KO₂, and NaO₂ are prepared by the direct reaction of O₂ with the respective alkali metal.^[2] The O-O bond distance in O₂⁻ is 1.33 Å, vs. 1.21 Å in O₂ and 1.49 Å in O₂²⁻. The overall trend corresponds to a reduction in the bond order from 2 (O₂), to 1.5 (O₂⁻), to 1 (O₂²⁻). Superoxides are compounds in which oxidation number of oxygen is -1/2. Potassium superoxide (symbol KO2) is a superoxide of potassium. ... Sodium superoxide has formula NaO2. ... In chemical nomenclature, the oxidation number (formerly known as the Stock number) of an element in a molecule or complex is the charge that it would bear if all the ligands were removed along with the electron pairs that were shared with the central atom. ...

The alkali salts of O₂⁻ are orange-yellow in color and quite stable, provided they are kept dry, Upon dissolution of these salts in water, however, the dissolved O₂⁻ decomposes (dismutates) extremely rapidly:

2 O₂⁻ + 2 H₂O → O₂ + H₂O₂ + 2 OH⁻

In this process O₂⁻ acts as a strong Brønsted base, initially forming HO₂. The pKa of its conjugate acid, hydrogen superoxide (HO₂, also known as "hydroperoxyl" or "perhydroxy radical"), is 4.88 so that at neutral pH 7 the vast majority of superoxide in the anionic form O₂⁻. An acid-base reaction is a chemical reaction between an acid and a base. ... In chemistry and biochemistry, acid dissociation constant, the acidity constant, or the acid-ionization constant () is a specific type of equilibrium constant that indicates the extent of dissociation of hydrogen ions from an acid. ... Within the Brønsted-Lowry (protonic) theory of acids and bases, a conjugate acid is the acid member, HX, of a pair of two compounds that transform into each other by gain or loss of a proton. ... The correct title of this article is . ...

Salts also decompose in the solid state, but this process requires heating:

2NaO₂ → Na₂O₂ + O₂

This reaction is the basis of the use of potassium superoxide as an oxygen source in chemical oxygen generators, such as those used on the space shuttle and on submarines. Potassium superoxide (symbol KO2) is a superoxide of potassium. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... A chemical oxygen generator is a device that releases oxygen created by a chemical reaction. ... NASAs Space Shuttle, officially called Space Transportation System (STS), is the United States governments current manned launch vehicle. ... German UC-1 class World War I submarine A model of Günther Priens Unterseeboot 47 (U-47), German WWII Type VII diesel-electric hunter Typhoon class nuclear ballistic missile submarine USS Virginia, a Virginia-class nuclear attack (SSN) submarine A submarine is a specialized watercraft that can operate...

Biology and superoxide

Superoxide is biologically quite toxic and is deployed by the immune system to kill invading microorganisms. In phagocytes, superoxide is produced in large quantities by the enzyme NADPH oxidase for use in oxygen-dependent killing mechanisms of invading pathogens. Mutations in the gene coding for the NADPH oxidase cause an immunodeficiency syndrome called chronic granulomatous disease, characterized by extreme susceptibility to infection. Superoxide is also deleteriously produced as a byproduct of mitochondrial respiration (most notably by Complex I and Complex III), as well as several other enzymes, for example xanthine oxidase. A scanning electron microscope image of a single human lymphocyte. ... A cluster of Escherichia colibacteria magnified 10,000 times. ... A phagocyte is a cell that ingests and destroys foreign matter such as microorganisms or debris via a process known as phagocytosis, in which these cells ingest and kill offending cells by a process analogous to cellular digestion, usually using lysosomes which carry potent enzymes that digests cell components such... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... The NADPH oxidase (nicotinamide adenine dinucleotide phosphate-oxidase) complex is an enzyme complex that is made up of five subunits. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... In medicine (genetics and pediatrics) chronic granulomatous disease (CGD) is a hereditary disease where neutrophil granulocytes are unable to destroy ingested pathogens. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Cellular respiration is a process that describes the metabolic reactions and processes that take place in a cell to obtain chemical energy from fuel molecules. ... NADH dehydrogenase NADH dehydrogenase (EC 1. ... schematic illustration of complex III reactions The coenzyme Q : cytochrome c — oxidoreductase, sometimes called the cytochrome bc1 complex, and at other times complex III, is the third complex in the electron transport chain (EC 1. ... Xanthine Oxidase The enzyme xanthine oxidase, or XO, (bovine milk enzyme is PDB 1FIQ, EC 1. ...

The biological toxicity of superoxide is due to its capacity to inactivate iron-sulfur cluster containing enzymes (which are critical in a wide variety of metabolic pathways), thereby liberating free iron in the cell, which can undergo fenton-chemistry and generate the highly reactive hydroxyl radical. In its HO₂ form, superoxide can also initiate lipid peroxidation of polyunsaturated fatty acids. It also reacts with carbonyl compounds and halogenated carbons to create toxic peroxy radicals. As such, superoxide is a main cause of oxidative stress. General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Lipids are a class of hydrocarbon-containing organic compounds. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid often with a long unbranched aliphatic tail (chain), which is either saturated or unsaturated. ... Carbonyl group In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom. ... The halogens are a chemical series of nonmetals. ... Oxidative stress is a medical term for damage to animal or plant cells (and thereby the organs and tissues composed of those cells) caused by reactive oxygen species, which include (but are not limited to) superoxide, singlet oxygen, peroxynitrite or hydrogen peroxide. ...

Because superoxide is toxic, nearly all organisms living in the presence of oxygen contain isoforms of the superoxide scavenging enzyme, superoxide dismutase, or SOD. SOD is an extremely efficient enzyme; it catalyzes the neutralization of superoxide nearly as fast as the two can diffuse together spontaneously in solution. Genetic inactivation ("knockout") of SOD produces deleterious phenotypes in organisms ranging from bacteria to mice. The latter species dies around 21 days after birth if the mitochondrial variant of SOD (Mn-SOD) is inactivated, and suffers from multiple pathologies, including reduced lifespan, liver cancer, muscle atrophy, cataracts and female infertility when the cytoplasmic (Cu,Zn-SOD) variant is inactivated. In biology, a protein isoform is a version of a protein with some small differences, usually a splice variant or the product of some posttranslational modification. ... Superoxide dismutase The enzyme superoxide dismutase (SOD, EC 1. ... Individuals in the mollusk species Donax variabilis show diverse coloration and patterning in their phenotypes. ... In cell biology, a mitochondrion is an organelle found in the cells of most eukaryotes. ... Hepatic tumors are tumors or growths on or in the liver (medical terms pertaining to the liver often start in hepato- or hepatic from the Greek word for liver, hepar). ... Organelles. ...

References

1. ^ Sawyer, D. T. Superoxide Chemistry, McGraw-Hill, DOI:10.1036/1097-8542.669650
2. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.

A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ...

Other reading

• McCord, J. M.; Fridovich, I. Superoxide dismutase. An enzymic function for erythrocuprein (hemocuprein). J. Biol. Chem. 244:6049-6055.; 1969.
• Li, Y. et al. Dilated cardiomyopathy and neonatal lethality in mutant mice lacking manganese superoxide dismutase. Nat. Genet. 11:376-381; 1995.
• Elchuri, S. et al. CuZnSOD deficiency leads to persistent and widespread oxidative damage and hepatocarcinogenesis later in life. Oncogene 24:367-380; 2005.
• Muller, F. L.; et al. Absence of CuZn superoxide dismutase leads to elevated oxidative stress and acceleration of age-dependent skeletal muscle atrophy. Free Radic. Biol. Med. 40:1993-2004; 2006.

See also

• ozonide, O₃⁻
• superoxide, O₂⁻
• peroxide, O₂²⁻
• oxide, O²⁻
• dioxygenyl, O₂⁺
• Antimycin A - used in fishery management, this compund produces large quantities of this free radical.