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In atmospheric chemistry, the most common scavenger is the hydroxyl radical, a short-lived radical produced photolytically in the atmosphere. It is the most important oxidant for carbon monoxide, methane and other hydrocarbons, sulfur dioxide, hydrogen sulfide, and most of other contaminants, removing them from the atmosphere.
The oxidation of 2,4,6-tri-tert-butylphenol in the alkaline to the intensely blue-colored phenoxy radical can also occur with potassium ferricyanide. [1] [9] [6] The 2,4,6-tri-tert-butylphenoxy radical forms blue crystals on cooling to -70 °C which are stable at room temperature for several weeks and only gradually turn yellow. [9]
Example structure of a HAL. The ability of hindered amine light stabilizers (HALS or HAS) to scavenge radicals produced by weathering, may be explained by the formation of aminoxyl radicals through a process known as the Denisov Cycle. The aminoxyl radical (N-O•) combines with free radicals in polymers: N-O• + R• → N-O-R
Thiyl radicals (sulfur-centred) can transform to carbon-centred radicals via hydrogen atom exchange equilibria. The formation of carbon-centred radicals could lead to protein damage via the formation of C−C bonds or backbone fragmentation. [36] Because of the weakness of the S−H bond, thiols can function as scavengers of free radicals. [37]
The hydroxyl radical, Lewis structure shown, contains one unpaired electron. Lewis dot structure of a Hydroxide ion compared to a hydroxyl radical. In chemistry, a radical, also known as a free radical, is an atom, molecule, or ion that has at least one unpaired valence electron.
Thioesters: Act by decomposing peroxides into non-radical products. Thioesters are also used as co-stabilisers with primary antioxidants. [citation needed] Hindered Amine Light Stabilizers (HALS): HALS act by scavenging free radicals generated during photo-oxidation, thus preventing the polymer material from UV radiation. [citation needed]
Examples are homopolymers of C 60-polystyrene [30] ... It is a very good scavenger of free radicals, and it can be used for controlling radical polymerizations.
The radical cyclization step usually involves the attack of a radical on a multiple bond. After this step occurs, the resulting cyclized radicals are quenched through the action of a radical scavenger, a fragmentation process, or an electron-transfer reaction. Five- and six-membered rings are the most common products; formation of smaller and ...