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Radical elimination can be viewed as the reverse of radical addition. In radical elimination, an unstable radical compound breaks down into a spin-paired molecule and a new radical compound. Shown below is an example of a radical elimination reaction, where a benzoyloxy radical breaks down into a phenyl radical and a carbon dioxide molecule. [7]
Bredt's rule also applies to carbocations and, to a lesser degree, free radicals, because these intermediates also prefer a planar geometry with 120° angles and sp 2 hybridization. It generally does not apply to hypervalent heteroatoms , although they are commonly written with a formal double bond.
For example, when polystyrene decomposes upon heating at a temperature above 300 °C, a styrene monomer is generated via a radical elimination mechanism (See Fig. 2). [2] Here, the new radical is generated on the polymer chain, which can further undergo a similar type of reaction to generate more styrene molecules.
Radicals can propagate (k p) but also terminate (k t). However, persistent radicals (X), as stated above, cannot terminate with each other but only (reversibly) cross-couple with the growing species (k deact). Thus, every act of radical–radical termination is accompanied by the irreversible accumulation of X. Consequently, the concentration ...
Radical disproportionation encompasses a group of reactions in organic chemistry in which two radicals react to form two different non-radical products. Radicals in chemistry are defined as reactive atoms or molecules that contain an unpaired electron or electrons in an open shell. The unpaired electrons can cause radicals to be unstable and ...
Another example is Kolbe electrolysis. Radical-nucleophilic aromatic substitution is a special case of nucleophilic aromatic substitution. Carbon–carbon coupling reactions, for example manganese-mediated coupling reactions. Elimination reactions; Free radicals can be formed by photochemical reaction and thermal fission reaction or by ...
Chain propagation: A radical reacts with a non-radical to produce a new radical species; Chain termination: Two radicals react with each other to create a non-radical species; In a free-radical addition, there are two chain propagation steps. In one, the adding radical attaches to a multiply-bonded precursor to give a radical with lesser bond ...
In free radical polymerization, radicals formed from the decomposition of an initiator molecule are surrounded by a cage consisting of solvent and/or monomer molecules. [6] Within the cage, the free radicals undergo many collisions leading to their recombination or mutual deactivation. [5] [6] [9] This can be described by the following reaction: