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Radical disproportionation : ウィキペディア英語版 | Radical disproportionation Radicals in chemistry are defined as reactive atoms or molecules that contain unpaired electrons in an open shell. The unpaired electrons cause radicals to be unstable and reactive. Reactions in radical chemistry can generate both radical and non-radical products. Radical disproportionation encompasses a group of reactions in organic chemistry in which two radicals react to form two different non-radical products. These reactions can occur with many radicals in solution and in the gas phase. Due to the unstable nature of radical molecules, disproportionation proceeds rapidly and requires little to no activation energy.〔Thommarson, R. L. ''J. Phys. Chem.'', 1970, ''74'', 938-941. 〕 The most thoroughly studied radical disproportionation reactions have been conducted with alkyl radicals, but there are many organic molecules that can exhibit more complex, multi-step disproportionation reactions. ==Mechanism of Radical Disproportionation== In radical disproportionation reactions one molecule acts as an acceptor while the other molecule acts as a donor.〔Benson, Sidney W. ''J. Phys. Chem.'', 1985, ''89'', 4366-4369. 〕 In the most common disproportionation reactions, a hydrogen atom is taken, or abstracted by the acceptor as the donor molecule undergoes an elimination reaction to form a double bond.〔Kelley, Richard D., Klein, Ralph. ''J. Phys. Chem.'', 1974, ''78'', 1586-1595. 〕 Other atoms such as halogens may also be abstracted during a disproportionation reaction.〔Setser, D. W., Muravyov, A. A., Rengarajan, R. ''J. Phys. Chem.'', 2004, ''108'', 3745-3755. 〕 Abstraction occurs as a head to tail reaction with the atom that is being abstracted facing the radical atom on the other molecule. center
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