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The stability of many (or most) organic radicals is not indicated by their isolability but is manifested in their ability to function as donors of H •. This property reflects a weakened bond to hydrogen, usually O−H but sometimes N−H or C−H. This behavior is important because these H • donors serve as antioxidants in biology and in ...
The ethoxy and cyano groups are able to delocalize the radical ion in the transition state, thus stabilizing the radical center. The rate enhancement is due to the captodative effect. When R = H, the reaction has the largest energy of activation because the radical center is not stabilized by the captodative effect.
Radicals decrease in stability as they are closer to the nucleus, because the electron affinity of the orbital increases. As a general rule, hybridizations minimizing s-character increase the stability of radicals, and decreases the bond dissociation energy (i.e. sp 3 hybridization is most stabilizing). [6]
Most notably hydroxyl radicals are produced from the decomposition of hydroperoxides (ROOH) or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. It is also an important radical formed in radiation chemistry, since it leads to the formation of hydrogen peroxide and oxygen, which can enhance corrosion and stress ...
In 2017, N-heterocyclic carbene-stabilized phosphorus-centered diradicals were reported; like the Niecke-type diradicaloid, the core heterocycle is a [P 2 C 2] four-membered ring, but the radical centers are located on phosphorus rather than carbon. [37] Lastly, one of the first hetero-cyclobutanediyl derivates synthesized is N 2 S 2, disulfur ...
Hyperconjugation can be used to rationalize a variety of chemical phenomena, including the anomeric effect, the gauche effect, the rotational barrier of ethane, the beta-silicon effect, the vibrational frequency of exocyclic carbonyl groups, and the relative stability of substituted carbocations and substituted carbon centred radicals, and the thermodynamic Zaitsev's rule for alkene stability.
For example, AIBN and ABCN yield isobutyronitrile and cyclohexanecarbonitrile radicals, respectively. Organic peroxides each have a peroxide bond (-O-O-), which is readily cleaved to give two oxygen-centered radicals. The oxyl radicals are unstable and believed to be transformed into relatively stable carbon-centered radicals.
N-Bromosuccinimide or NBS is a chemical reagent used in radical substitution, electrophilic addition, and electrophilic substitution reactions in organic chemistry. NBS can be a convenient source of Br •, the bromine radical. [1]