Captodative effect

According to the captodative effect, the rate of a reaction is the greatest when both the EDG and EWG are able to delocalize the radical ion in the transition state structure.

[7] Ito and co-workers observed the rate of addition reactions of aryl thiol radical to disubstituted olefins.

Thus, the captodative does not influence the reaction rate if the radical ion is not delocalized onto both the EWG and EDG substituents.

Each of these cases is illustrated below: The term "captodative ethylenes" has been used in the context of cycloaddition reactions involving captodative radical intermediates – for example, the thermal [2+2] head-to-head dimerization of 2-methylthioacrylonitrile occurs readily at room temperature; formation of the equivalent cyclobutane derivative of acrylonitrile is "sluggish".

[4] They have also shown to undergo their radical transformation spontaneously which allows them to be useful in polymerization mechanism elucidation and better understood through NMR Studies.

Furthermore, captodative ethanes are initiators with unique properties giving higher molecular weight distribution and forming block copolymers through the known radical mechanisms.

The polymers obtained from captodatively substituted starting materials exhibit "desirable" properties such as optical activity, differences in polarity, solvent affinity, thermal and mechanical stabilities.