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In order to repeat the reaction, the electron in the reaction center needs to be replenished. This occurs by oxidation of water in the case of oxygenic photosynthesis. The electron-deficient reaction center of photosystem II (P680*) is the strongest biological oxidizing agent yet discovered, which allows it to break apart molecules as stable as ...
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).
Two further early examples were the rearrangement of 1,1,5,5-tetraphenyl-3,3-dimethyl-1,4-pentadiene (the "Mariano" molecule) [22] and the rearrangement of barrelene to semibullvalene. [23] We note that, in contrast to the cyclohexadienone reactions which used n-π * excited states, the di-π-methane rearrangements utilize π-π * excited states.
In one mechanism of the oxidative reaction, holes react with the moisture present on the surface and produce a hydroxyl radical. The reaction starts by photo-induced exciton generation in the metal oxide (MO) surface by photon (hv) absorption: MO + hν → MO (h + + e −) Oxidative reactions due to photocatalytic effect: h + + H 2 O → H ...
Photo-oxidation is a form of photodegradation and begins with formation of free radicals on the polymer chain, which then react with oxygen in chain reactions. For many polymers the general autoxidation mechanism is a reasonable approximation of the underlying chemistry.
An example of a synthetically useful Norrish type II reaction can be found early in the total synthesis of the biologically active cardenolide ouabagenin by Phil Baran and coworkers. [15] The optimized conditions minimize side reactions, such as the competing Norrish type I pathway, and furnish the desired intermediate in good yield on a multi ...
Synthetic photoinitiators are key components in photopolymers (for example, photo-curable coatings, adhesives and dental restoratives). Some small molecules in the atmosphere can also act as photoinitiators by decomposing to give free radicals (in photochemical smog).
It cannot carry out reactions in the form of n CO 2 + 2n H 2 D + photons → (CH 2 O) n + 2n D + n H 2 O, where H 2 D may be water, H 2 S or another compound/compounds providing the reducing electrons and protons; the 2D + H 2 O pair represents an oxidized form. However, it can fix carbon in reactions like: CO 2 + pyruvate + ATP (from photons ...