Hydroxyl radical in the context of "Hydroxyl group"

Hydroxide is a diatomic anion with chemical formula OH. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical.The corresponding electrically neutral compound HO is the hydroxyl radical. The corresponding covalently bound group −OH of atoms is the hydroxy group.Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry.

Many inorganic substances which bear the word hydroxide in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups.

In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula −OH and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy groups. Both the negatively charged anion HO, called hydroxide, and the neutral radical HO·, known as the hydroxyl radical, consist of an unbonded hydroxy group.

According to IUPAC definitions, the term hydroxyl refers to the hydroxyl radical (·OH) only, while the functional group −OH is called a hydroxy group.

In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.

A notable example of a radical is the hydroxyl radical (HO·), a molecule that has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (꞉CH
₂) which have two unpaired electrons.

Advanced oxidation processes (AOPs), in a broad sense, are a set of chemical treatment procedures designed to remove organic (and sometimes inorganic) materials in water and wastewater by oxidation through reactions with hydroxyl radicals (·OH). In practice within wastewater treatment, this term usually refers more specifically to a subset of such chemical processes that employ ozone (O₃), hydrogen peroxide (H₂O₂) and UV light or a combination of the few processes. Common AOP configurations often include Fenton and photo-Fenton systems, in addition to ozone/UV, TiO₂/UV photocatalysis, and Electro-Fenton systems.

In chemistry and biology, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (O₂), water, and hydrogen peroxide. Some prominent ROS are hydroperoxide, superoxide (O₂), hydroxyl radical (OH), and singlet oxygen(O₂). ROS are pervasive because they are readily produced from O₂, which is abundant. ROS are important in many ways, both beneficial and otherwise. ROS function as signals, that turn on and off biological functions. They are intermediates in the redox behavior of O₂, which is central to fuel cells. ROS are central to the photodegradation of organic pollutants in the atmosphere. Most often, however, ROS are discussed in a biological context, ranging from their effects on aging and their role in causing dangerous genetic mutations.