Lesson plan
Captodative effect
The captodative effect is the stabilization of radicals by a synergistic effect of an electron-withdrawing substituent and an electron-donating substituent. The name originates as the electron-withdrawing group (EWG) is sometimes called the "captor" group, whilst the electron-donating group (EDG) is the "dative" substituent. Olefins with this substituent pattern are sometime described as captodative. Radical reactions play an integral role in several chemical reactions and are also important to the field of polymer science. When EDGs and EWGs are near the radical center, the stability of the radical center increases. The substituents can kinetically stabilize radical centers by preventing molecules and other radical centers from reacting with the center. The substituents thermodynamically stabilize the center by delocalizing the radical ion via resonance. These stabilization mechanisms lead to an enhanced rate for free-radicals that have these sorts of intermediates or transition states. In the figure at right, the radical is delocalized between the captor nitrile (-CN), and the dative secondary amine (-N(CH 3 ) 2 ), thus stabilizing the radical center. The stability of carbene radicals and carbene radical ligands has been rationalized and quantified by the captodative effect using the Klopman–Salem equation.
Article summary
The captodative effect is the stabilization of radicals by a synergistic effect of an electron-withdrawing substituent and an electron-donating substituent. The name originates as the electron-withdrawing group (EWG) is sometimes called the "captor" group, whilst the electron-donating group (EDG) is the "dative" substituent. Olefins with this substituent pattern are sometime described as captodative. Radical reactions play an integral role in several chemical reactions and are also important to the field of polymer science. When EDGs and EWGs are near the radical center, the stability of the radical center increases. The substituents can kinetically stabilize radical centers by preventing molecules and other radical centers from reacting with the center. The substituents thermodynamically stabilize the center by delocalizing the radical ion via resonance. These stabilization mechanisms lead to an enhanced rate for free-radicals that have these sorts of intermediates or transition states. In the figure at right, the radical is delocalized between the captor nitrile (-CN), and the dative secondary amine (-N(CH 3 ) 2 ), thus stabilizing the radical center. The stability of carbene radicals and carbene radical ligands has been rationalized and quantified by the captodative effect using the Klopman–Salem equation.
Key claims
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Discussion questions
- Summarise the article in your own words. Which single claim would you verify first, and why?
- Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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Key claims and bibliography are generated from the same tracked claims and sources as the article page.