Captodative effect

<p>The captodative effect is the <a href="/facts/Chemical_stability/j0YIgc6F">stabilization</a> of <a href="/facts/Radical_(chemistry)/qFymuVoT">radicals</a> by a synergistic effect of an <a href="/facts/Polar_effect/GDzV1DXL">electron-withdrawing</a> <a href="/facts/Substituent/6y9IE6G0">substituent</a> 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. <a href="/facts/Olefin/RtYcS6kU">Olefins</a> 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 <a href="/facts/Polymer_science/ulLpdDyQ">polymer science</a>.
</p><p>When EDGs and EWGs are near the radical center, the stability of the radical center increases. The substituents can <a href="/facts/Chemical_kinetics/D8vyX4aE">kinetically</a> stabilize radical centers by preventing <a href="/facts/Molecule/N9ljSfFq">molecules</a> and other radical centers from reacting with the center. The substituents thermodynamically stabilize the center by delocalizing the radical ion via <a href="/facts/Resonance_(chemistry)/5tymwoIP">resonance</a>. These stabilization mechanisms lead to an enhanced rate for free-radical reactions. In the figure at right, the radical is delocalized between the captor <a href="/facts/Nitrile/Gz7RCnC6">nitrile</a> (-CN), and the dative secondary <a href="/facts/Amine/JvfYJfP6">amine</a> (-N(CH3)2), thus stabilizing the radical center.
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Captodative effect open-in-new

Captodative effect