hydroxyl

The univalent radical or group OH, a characteristic component of bases, certain acids, phenols, alcohols, carboxylic and sulfonic acids, and amphoteric compounds.

[HYDR(O)- + OX(YGEN) + -YL.]

A chemical group in which oxygen and hydrogen are bonded and act as a single entity. In inorganic chemistry the hydroxyl group is known as the hydroxide ion (OH⁻), and it is frequently bonded to metal cations, for example, sodium hydroxide (NaOH). In organic chemistry it frequently acts as a functional group, for example, in an alcohol (ROH, where R represents an alkyl group). See also Acid and base.

Many of the intermediate redox forms of dioxygen are toxic and damage important biomolecules. Much of this toxicity is thought to involve the generation and reactivity of hydroxyl (·OH), which is sometimes called the hydroxy radical. The most common means for producing hydroxyl is the reaction of a reducing agent with hydrogen peroxide (H₂O₂). Transition-metal ions, such as ferrous ion (Fe²⁺), are the most common reducing agents for generating ·OH.

Once generated, hydroxyl is a potent one-electron oxidant that forms the very stable OH⁻ ion, and it abstracts hydrogen atoms from organic molecules that contain CH bonds to form the stronger OH bond in water. The reaction of a radical, which contains an uneven number of electrons, with a molecule, which contains an even number of electrons paired in bonds, must generate a radical, because the number of electrons cannot change during the reaction. Thus, most reactions of radicals generate new radicals in processes called radical chain reactions. Reactions of radicals with molecules will continue to produce new radicals until other odd-electron species (such as transition-metal ions or other radicals) react with the radicals to produce even-electron molecules via termination reactions. See also Chain reaction (chemistry); Transition elements.

The univalent radical −OH.

This article is about the hydroxyl functional group. For the Hydroxyl radical, see Hydroxyl radical.

In chemistry, hydroxyl is composed of molecules consisting of an oxygen atom and a hydrogen atom connected by a covalent bond (single bond). The neutral form is a hydroxyl radical. The hydroxyl anion (OH⁻) is called hydroxide; it is a diatomic ion with a charge of negative one. When linked to a larger molecule the hydroxyl group is a functional group (–OH).

Contents 1 Hydroxyl group 2 Hydroxyl radical 3 Lunar discovery 4 See also 5 References

Hydroxyl group

The term hydroxyl group is used to describe the functional group –OH when it is a substituent in an organic compound. Organic molecules containing a hydroxyl group are known as alcohols (the simplest of which have the formula C_nH_2n+1–OH).

Hydroxyl radical

3D model of hydroxyl group.

Main article: Hydroxyl radical

The hydroxyl radical, ·OH, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and, as a consequence, short-lived; however, they form an important part of radical chemistry.

Hydroxyl free radicals cause damage to oxidative cells, particularly erythrocytes (or red blood cells). These free radicals can damage DNA, lipids, and proteins.^{[citation needed]} Glucose-6 phosphate dehydrogenase (G6PD) is an enzyme the body produces to destroy OH-, before it starts damaging the cells. People with G6PD deficiency are protected against malaria because the plasmodium (the parasites that cause malaria) cannot survive in the damaged blood cells.^{[citation needed]} On the other hand, people with G6PD deficiency are prone to jaundice and kidney disease.^{[citation needed]}

Lunar discovery

In the September 24, 2009 issue of the scientific journal Science, it was reported that India's Chandrayaan-1 satellite, NASA's Cassini spacecraft and Deep Impact probe have all detected the presence of water and hydroxyl on the moon. As reported by Richard Kerr, "A spectrometer (the Moon Mineralogy Mapper, aka "M3"), detected an infrared absorption at a wavelength of 3.0 micrometers that only water or hydroxyl–a hydrogen and an oxygen bound together–could have created."^[1]

See also

Look up hydroxyl in Wiktionary, the free dictionary.

• Hydronium
• Oxide
• Hydroxy

References

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2009)

1. ^ http://sciencenow.sciencemag.org/cgi/content/full/2009/924/1

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