WordNet
n. the monovalent group -OH in such compounds as bases and some acids and alcohols [syn: hydroxyl, hydroxyl group]
Wikipedia
The hydroxyl radical, OH, is the neutral form of the hydroxide ion (OH). Hydroxyl radicals are highly reactive (easily becoming hydroxyl groups) and consequently short-lived; however, they form an important part of radical chemistry. Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides (ROOH) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also an important radical formed in radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and SCC in coolant systems subjected to radioactive environments. Hydroxyl radicals are also produced during UV-light dissociation of HO (suggested in 1879) and likely in Fenton chemistry, where trace amounts of reduced transition metals catalyze peroxide-mediated oxidations of organic compounds.
In organic synthesis, hydroxyl radicals are most commonly generated by photolysis of 1-hydroxy-2(1H)-pyridinethione.
The hydroxyl radical is often referred to as the "detergent" of the troposphere because it reacts with many pollutants, decomposing them through " cracking", often acting as the first step to their removal. It also has an important role in eliminating some greenhouse gases like methane and ozone. The rate of reaction with the hydroxyl radical often determines how long many pollutants last in the atmosphere, if they do not undergo photolysis or are rained out. For instance methane, which reacts relatively slowly with hydroxyl radical, has an average lifetime of >5 years and many CFCs have lifetimes of 50 years or more. Pollutants, such as larger hydrocarbons, can have very short average lifetimes of less than a few hours.
The first reaction with many volatile organic compounds (VOCs) is the removal of a hydrogen atom, forming water and an alkyl radical (R).
OH + RH → HO + RThe alkyl radical will typically react rapidly with oxygen forming a peroxy radical.
R + O → ROThe fate of this radical in the troposphere is dependent on factors such as the amount of sunlight, pollution in the atmosphere and the nature of the alkyl radical that formed it.
Usage examples of "hydroxyl radical".
One of the four nucleotides in the DNA has a hydroxyl radical where DNA nucleotides on Earth just have a hydrogen ion.
Together, hydrogen and the hydroxyl radical combine to form water, the basis for all life as we know it.
They were found mostly in the part of the spectrum between the hydrogen and hydroxyl radical lines, where theory had long predicted that water-based life would be apt to concentrate its communication efforts.
The distributed observing system around the L-4 Argus Station still explored the ancient water-hole of the early investigators, between the spectral lines of neutral hydrogen and the hydroxyl radical, and to that they had added the preferred zone of neutrino resonance capture, a region undreamed of in early SETI work.
The space between the emissions of interstellar hydrogen and hydroxyl radical at round about 1420 MHz.