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Photochemical immersion well reactor (50 mL) with a mercury-vapor lamp.. Photochemistry is the branch of chemistry concerned with the chemical effects of light. Generally, this term is used to describe a chemical reaction caused by absorption of ultraviolet (wavelength from 100 to 400 nm), visible (400–750 nm), or infrared radiation (750–2500 nm).
Photodissociation, photolysis, photodecomposition, or photofragmentation is a chemical reaction in which molecules of a chemical compound are broken down by absorption of light or photons. It is defined as the interaction of one or more photons with one target molecule that dissociates into two fragments. [1]
PAN is produced in the atmosphere via photochemical oxidation of hydrocarbons to peroxyacetic acid radicals, which react reversibly with nitrogen dioxide (NO 2) to form PAN. [4]: 2680 Night-time reaction of acetaldehyde with nitrogen trioxide is another possible source. [4] Since there are no direct emissions, it is a secondary pollutant.
The Barton reaction involves a homolytic RO–NO cleavage, followed by δ-hydrogen abstraction, free radical recombination, and tautomerization to form an oxime. [3] Selectivity for the δ-hydrogen is a result of the conformation of the 6-membered radical intermediate. Often, the site of hydrogen atom abstraction can be easily predicted.
Photochemical reactions are initiated by the absorption of a photon, typically in the wavelength range 290–700 nm (at the surface of the Earth). The energy of an absorbed photon is transferred to electrons in the molecule and briefly changes their configuration (i.e., promotes the molecule from a ground state to an excited state). The excited ...
The hydroxyl • HO radicals is one of the main chemical species controlling the oxidizing capacity of the Earth's atmosphere, having a major impact on the concentrations and distribution of greenhouse gases and pollutants. It is the most widespread oxidizer in the troposphere, the lowest part of the atmosphere.
Photosynthetic water splitting (or oxygen evolution) is one of the most important reactions on the planet, since it is the source of nearly all the atmosphere's oxygen. Moreover, artificial photosynthetic water-splitting may contribute to the effective use of sunlight as an alternative energy-source.
A Norrish type II reaction is the photochemical intramolecular abstraction of a γ-hydrogen (a hydrogen atom three carbon positions removed from the carbonyl group) by the excited carbonyl compound to produce a 1,4-biradical as a primary photoproduct. [9] Norrish first reported the reaction in 1937. [10] Norrish type II reaction