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In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron. [ 1][ 2] With some exceptions, these unpaired electrons make radicals highly chemically reactive. Many radicals spontaneously dimerize. Most organic radicals have short lifetimes.
Free-radical addition. In organic chemistry, free-radical addition is an addition reaction which involves free radicals. Radical additions are known for a variety of unsaturated substrates, both olefinic or aromatic and with or without heteroatoms. Free-radical reactions depend on one or more relatively weak bonds in a reagent.
In polymer chemistry, the kinetic chain length ( ν) of a polymer is the average number of units called monomers added to a growing chain during chain-growth polymerization. During this process, a polymer chain is formed when monomers are bonded together to form long chains known as polymers. Kinetic chain length is defined as the average ...
A free-radical reaction is any chemical reaction involving free radicals. This reaction type is abundant in organic reactions. Two pioneering studies into free radical reactions have been the discovery of the triphenylmethyl radical by Moses Gomberg (1900) and the lead-mirror experiment[ 1] described by Friedrich Paneth in 1927.
The hydroxyl radical, •HO, is the neutral form of the hydroxide ion (HO – ). Hydroxyl radicals are highly reactive 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 ...
Nitric oxide ( nitrogen oxide or nitrogen monoxide[ 1]) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula ( • N=O or • NO).
Free-radical halogenation. In organic chemistry, free-radical halogenation is a type of halogenation. This chemical reaction is typical of alkanes and alkyl -substituted aromatics under application of UV light. The reaction is used for the industrial synthesis of chloroform (CHCl 3 ), dichloromethane (CH 2 Cl 2 ), and hexachlorobutadiene.
t. e. In polymer chemistry, free-radical polymerization ( FRP) is a method of polymerization by which a polymer forms by the successive addition of free-radical building blocks ( repeat units ). Free radicals can be formed by a number of different mechanisms, usually involving separate initiator molecules.