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Captodative effect is the phenomenon associated with the stabilization of radicals by their substituents – one of these substituents being an electron-withdrawing group (EWG), the "captor", and the other an electron-donating group (EDG), the donor or "dative" substituent. These two work in tandem to enhance the stabilization of the radical center of molecules in free radical reactions.^[1] 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. ^[2] The substituents can kinetically stabilize radical centers by preventing molecules and other radical centers from reacting with the center.^[1] The substituents thermodynamically stabilize the center by delocalizing the radical ion via resonance.^[1]^[2] These stabilization mechanisms lead to an enhanced rate for free radical reactions.^[3]

File:Resonance contributors of 2-(dimethylamino)propanenitrile.jpg

The resonance contributors of this free radical cause it be very stable via the captodative effect, adapted from Anslyn^[2]

In the above figure the radical is delocalized between the EWG, a nitrile (-CN), and the EDG, a secondary amine (-N(CH₃)₂),^[1] thus stabilizing the radical center.

Substituent effect on reaction rates

Certain substituents are better at stabilizing radical centers than others.^[4] This is influenced by the substituent's ability to delocalize the radical ion in the transition state structure.^[1] Delocalizing the radical ion stabilizes the transition state structure. As a result, the energy of activation decreases, enhancing the rate of the overall reaction. 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.^[5]

Ito and co-workers observed the rate of addition reactions of arylthiyl radical to disubstituted olefins.^[4] The olefins contained an EWG, a cyan group and varying EDGs. The authors observed how the varying EDGs effect the rate of the addition reactions.

File:General Reaction Scheme.png

General schematic of the addition reaction of arylthiyl radicals to captodative olefins.

The rate of the addition reaction was accelerated by the following EDGs in increasing order: H < CH₃ < OCH₂CH₃. When R=OCH₂CH₃, the rate of the reaction is the fastest because the reaction has the smallest energy of activation (ΔG^‡). The -OCH₂CH₃ and the cyano group are able to delocalize the radical ion in the transition, 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. The hydrogen atom is not able to delocalize the radical ion. Thus, the reaction is slow relative to when R = OCH₂CH₃. When R = CH₃, the rate of the reaction is faster relative to when R = H because methyl groups have more electron donating capability.^[4] However, when the reaction rate is slower relative to when R = OCH₂CH₃ because the radical ion is not delocalized the methyl group groups. Thus, the captodative does not influence the reaction rate if the radical ion is not delocalized onto both the EWG and EDG substituents.

File:New Transition State.png

Various electron-donating groups (shown in red) can affect the rate of the addition reactions of arythiyl radicals to captodative olefins

Uses in synthesis

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".^[6] Intramolecular [2+2] cyclizations have also been reported to be enhanced by captodative effects,^[6] as shown below:

File:2plus2 cyclodimerisation and intramolecular cyclisation of captodative olefins.jpg

Similar effects have been discussed for other cycloadditions such as [3+2], [4+2], and [3+4] for captodative ethylenes.^[7] Effects have also been reported in cases like Diels-Alder and Friedel-Crafts reactions in cases where nucleophilic olefins react inefficiently, attributed to the transition state being close to a biradical and thus stabilized.^[6]^[8] These studies have revealed a direct dependence on Δω, difference in electrophilicity, and the polar nature of the reaction. They have been used because of their highly reactive, stereoselective, regioselective nature within these reactions.^[7]^[9]

File:Diels Alder.png

File:Friedel Craft Reaction.png

Captodative olefins in reactions also show interfering effects with the typical kinetic isotope effect, allowing atypical reactions to occur with isotope-labeled molecules^[10] and demonstrating that the mechanisms and transition states of these reactions has been influenced.

Polymer science application

Free radical polymerization, where radicals are the chain carriers in the propagation of the process, accounted for 40 billion of the 110 billion pounds of polymers produced in the United States in 2001.^[11] Captodative olefins have a specific advantage of being responsive to solvent effects without the effect of destabilizing the radical.^[12] 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.

Polymers with polar substituents are known to have interesting applications including within electrical and optical materials.
These polymers are typically transparent.
The T_di (initial decomposition) of these polymers are relatively low compared to their analogues, but have relatively higher T_dm (maximum rate of weight change temperatures). Meaning although they will start to melt quicker, they will take longer to fully change phases.
Polymers with large captodative stabilizations starting materials can quickly “unzip” to their starting monomer upon heating.
Bifunctional polymers, with two different functional groups at every monomer unit, are commonly formed from the captodative monomers.
1. Dative groups substantially alter the solubility through Hydrogen bonding in specific bifunctional polymers( see figure above). However no clear correlation has been developed at this time, since not all combinations of substituents and solubilities have been investigated.
Captodative polymer is highly functional in chelates with certain metals.^[13]

References

^ ^a ^b ^c ^d ^e Viehe, H. G.; Janousek, Z.; Merényi, R.; Stella, L. (1985). "The Captodative Effect". Accounts of Chemical Research. 18 (5): 148–154. doi:10.1021/ar00113a004.
^ ^a ^b ^c Anslyn, E. V.; Dougherty, D. A. (2006). Modern Physical Organic Chemistry (Dodr. ed.). Sausalito, CA: University Science Books. ISBN 9781891389313.
^ Sustmann, R.; Korth, H.-G. (1990). Advances in Physical Organic Chemistry. San Diego, CA: Academic Press. pp. 131–172. ISBN 0120335263.
^ ^a ^b ^c Ito, Osamu; Arito, Y.; Matsuda, M. (1988). "Captodative Effects on Rate of Addition Reactions of Arylthiyl Radical to Disubstituted Olefins". Journal of Chemical Society, Perkin Transaction 2: 869–873. doi:10.1039/P29880000869.
^ Creary, X.; Mehrisheikh-Mohammadi, M. E. (1985). "Captodative Rate Enhancement in the Methylenecyclopropane Rearrangement". Journal of Organic Chemistry. 51 (14): 2664–2668. doi:10.1021/jo00364a009.
^ ^a ^b ^c Stella, L. (1986). "Captodative Substituent Effects in Cycloaddition Reactions". In Viehe, H. G.; Janousek, Z.; Merényi, R. (eds.). Substituent Effects in Radical Chemistry. Springer. pp. 361–370. ISBN 9789027723406.
^ ^a ^b Herrera, R.; Jimenez-Vazquez, H. A.; Delgado, F.; Soderberg, B. C. G.; Tamariz, J. (2005). "1-Acetyvinyl Acrylates: New Captodative Olefins Bearing and Internal Probe for the Evaluation of the Relative Reactivity of Captodative against Electron-Deficient Double Bond in Diels-Alders and Friedel-Crafts Reaction". Journal of the Brazilian Chemical Society. 16 (3A): 456–466. doi:10.1590/S0103-50532005000300021.
^ Stella, L.; Boucher, J.-L. (1982). "Capto-dative Substituent Effects. 12¹ - New Ketene Equivalents for Diels-Alder Cycloadditions". Tetrahedron Letters. 22 (9): 953–956. doi:10.1016/S0040-4039(00)86992-0.
^ Domingo, L.; Chamorro, E.; Pérez, P. (2008). "Understanding the Reactivity of Captodative Ethylenes in Polar Cycloaddition Reactions. A Theoretical Study". Journal of Organic Chemistry. 73 (12): 4615–4624. doi:10.1021/jo800572a.
^ Wood, M.; Bissiriou, S.; Lowe, C.; Windeatt, K. M. (2013). "Synthetic Use of the Primary Kinetic Isotope Effect in Hydrogen Atom Transfer 2: Generation of Captodatively Stabilised Radicals". Organic and Biomolecular Chemistry. 11: 2712. doi:10.1039/C3OB40275D.
^ Odian, G. (2004). Principles of Polymerization (4th ed.). New York: Wiley-Interscience. ISBN 9780471274001.
^ Cite error: The named reference Tanaka was invoked but never defined (see the help page).
^ Tanaka, H. (2003). "Captodative Modification in Polymer Science". Progress in Polymer Science. 28 (7): 1171–1203. doi:10.1016/S0079-6700(03)00013-3.

[The_Captodative_Effect-1] Viehe, H. G.; Janousek, Z.; Merényi, R.; Stella, L. (1985). "The Captodative Effect". Accounts of Chemical Research. 18 (5): 148–154. doi:10.1021/ar00113a004.

[Physical_Organic_Book-2] Anslyn, E. V.; Dougherty, D. A. (2006). Modern Physical Organic Chemistry (Dodr. ed.). Sausalito, CA: University Science Books. ISBN 9781891389313.

[Advances_in_Physical_Organic_Chemistry-3] Sustmann, R.; Korth, H.-G. (1990). Advances in Physical Organic Chemistry. San Diego, CA: Academic Press. pp. 131–172. ISBN 0120335263.

[Rate_Enhancement_Olefins-4] Ito, Osamu; Arito, Y.; Matsuda, M. (1988). "Captodative Effects on Rate of Addition Reactions of Arylthiyl Radical to Disubstituted Olefins". Journal of Chemical Society, Perkin Transaction 2: 869–873. doi:10.1039/P29880000869.

[Rate_Enhancment_Methylenecyclopropane-5] Creary, X.; Mehrisheikh-Mohammadi, M. E. (1985). "Captodative Rate Enhancement in the Methylenecyclopropane Rearrangement". Journal of Organic Chemistry. 51 (14): 2664–2668. doi:10.1021/jo00364a009.

[Stella-6] Stella, L. (1986). "Captodative Substituent Effects in Cycloaddition Reactions". In Viehe, H. G.; Janousek, Z.; Merényi, R. (eds.). Substituent Effects in Radical Chemistry. Springer. pp. 361–370. ISBN 9789027723406.

[Friedel_Craft-7] Herrera, R.; Jimenez-Vazquez, H. A.; Delgado, F.; Soderberg, B. C. G.; Tamariz, J. (2005). "1-Acetyvinyl Acrylates: New Captodative Olefins Bearing and Internal Probe for the Evaluation of the Relative Reactivity of Captodative against Electron-Deficient Double Bond in Diels-Alders and Friedel-Crafts Reaction". Journal of the Brazilian Chemical Society. 16 (3A): 456–466. doi:10.1590/S0103-50532005000300021.

[8] Stella, L.; Boucher, J.-L. (1982). "Capto-dative Substituent Effects. 12¹ - New Ketene Equivalents for Diels-Alder Cycloadditions". Tetrahedron Letters. 22 (9): 953–956. doi:10.1016/S0040-4039(00)86992-0.

[9] Domingo, L.; Chamorro, E.; Pérez, P. (2008). "Understanding the Reactivity of Captodative Ethylenes in Polar Cycloaddition Reactions. A Theoretical Study". Journal of Organic Chemistry. 73 (12): 4615–4624. doi:10.1021/jo800572a.

[10] Wood, M.; Bissiriou, S.; Lowe, C.; Windeatt, K. M. (2013). "Synthetic Use of the Primary Kinetic Isotope Effect in Hydrogen Atom Transfer 2: Generation of Captodatively Stabilised Radicals". Organic and Biomolecular Chemistry. 11: 2712. doi:10.1039/C3OB40275D.

[11] Odian, G. (2004). Principles of Polymerization (4th ed.). New York: Wiley-Interscience. ISBN 9780471274001.

[Tanaka-12] Cite error: The named reference Tanaka was invoked but never defined (see the help page).

[4-13] Tanaka, H. (2003). "Captodative Modification in Polymer Science". Progress in Polymer Science. 28 (7): 1171–1203. doi:10.1016/S0079-6700(03)00013-3.

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-'''Captodative effect''' is the phenomenon associated with the [[Stabilizer (chemistry)|stabilization]] of [[Radical (chemistry)|radicals]] by their [[substituent]]s &ndash; one of these substituents being an [[Polar effect|electron-withdrawing]] group (EWG), the "captor", and the other an electron-donating group (EDG), the donor or "dative" substituent. These two work in tandem to enhance the stabilization of the radical center of molecules in free radical [[Chemical reaction|reactions]].<ref name="The Captodative Effect">{{cite journal|last=Viehe|first=Heinz G.|coauthors=Zdenek Janousek, Robert Merényi and Lucien Stella|title=The Captodative Effect|journal=Accounts of Chemical Research|year=1985|volume=18|pages=148–154|url=http://pubs.acs.org/doi/abs/10.1021/ar00113a004?journalCode=achre4}}</ref> Radical reactions play an integral role in several chemical reactions and are also important to the field of [[polymer science]].
+'''Captodative effect''' is the phenomenon associated with the [[Stabilizer (chemistry)|stabilization]] of [[Radical (chemistry)|radicals]] by their [[substituent]]s &ndash; one of these substituents being an [[Polar effect|electron-withdrawing]] group (EWG), the "captor", and the other an electron-donating group (EDG), the donor or "dative" substituent. These two work in tandem to enhance the stabilization of the radical center of molecules in free radical [[Chemical reaction|reactions]].<ref name="The Captodative Effect">{{cite journal|last1 = Viehe|first1 = H. G.|first2 = Z.|last2 = Janousek|first3 = R.|last3 = Merényi|first4 = L.|last4 = Stella|title = The Captodative Effect|journal = [[Accounts of Chemical Research]]|year = 1985|volume = 18|pages = 148–154|doi = 10.1021/ar00113a004|issue = 5}}</ref> 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. <ref name="Physical Organic Book" /> The substituents can [[Chemical kinetics|kinetically]] stabilize radical centers by preventing [[molecule]]s and other radical centers from reacting with the center.<ref name="The Captodative Effect" /> The substituents thermodynamically stabilize the center by delocalizing the radical ion via [[resonance (chemistry)|resonance]].<ref name="The Captodative Effect" /><ref name="Physical Organic Book">{{cite book|title=Modern physical organic chemistry|year=2006|publisher=University Science Books|location=Sausalito, Calif.|isbn=9781891389313|author= Eric V. Anslyn|coauthors=Dennis A. Dougherty |edition=Dodr.|url = http://books.google.com.au/books?id=gY-Sxijk_tMC&pg=PA573&lpg=PA573&dq=captodative+effect&source=bl&ots=etzKi9JqTh&sig=2LzHZHIULe-eyvUi1gP0AZrimaw&hl=en&sa=X&ei=Ddm2UribHIjJiAew2oHoDA&ved=0CFoQ6AEwBw#v=onepage&q=captodative%20effect&f=false}}</ref> These stabilization mechanisms lead to an enhanced rate for free radical reactions.<ref name="Advances in Physical Organic Chemistry">{{cite book|last=Sustmann|first=Reiner|coauthor=Hans-Gert Korth|title=Advances in Physical Organic Chemistry|year=1990|publisher=Academic Press Limited|location=San Diego, CA|isbn=0-12-033526-3|pages=131–172}}</ref>
+When EDGs and EWGs are near the radical center, the stability of the radical center increases. <ref name="Physical Organic Book" /> The substituents can [[Chemical kinetics|kinetically]] stabilize radical centers by preventing [[molecule]]s and other radical centers from reacting with the center.<ref name="The Captodative Effect" /> The substituents thermodynamically stabilize the center by delocalizing the radical ion via [[resonance (chemistry)|resonance]].<ref name="The Captodative Effect" /><ref name="Physical Organic Book">{{cite book|title = Modern Physical Organic Chemistry|year = 2006|publisher = University Science Books|location = Sausalito, CA|isbn = 9781891389313|author1-first = E. V.|author1-last = Anslyn|author2-first = D. A.|author2-last = Dougherty|edition = Dodr.|url = http://books.google.com.au/books?id=gY-Sxijk_tMC&pg=PA573&lpg=PA573&dq=captodative+effect&source=bl&ots=etzKi9JqTh&sig=2LzHZHIULe-eyvUi1gP0AZrimaw&hl=en&sa=X&ei=Ddm2UribHIjJiAew2oHoDA&ved=0CFoQ6AEwBw#v=onepage&q=captodative%20effect&f=false}}</ref> These stabilization mechanisms lead to an enhanced rate for free radical reactions.<ref name="Advances in Physical Organic Chemistry">{{cite book|author1-last = Sustmann|author1-first = R.|author2-first = H.-G.|author2-last = Korth|title = Advances in Physical Organic Chemistry|year = 1990|publisher = Academic Press|location = San Diego, CA|isbn = 0120335263|pages = 131–172}}</ref>
 [[File:Resonance contributors of 2-(dimethylamino)propanenitrile.jpg|thumb|400px|center|The resonance contributors of this free radical cause it be very stable via the captodative effect, adapted from Anslyn<ref name="Physical Organic Book" />]]
@@ Line 7: / Line 7: @@
 ==Substituent effect on reaction rates==
-Certain substituents are better at stabilizing radical centers than others.<ref name="Rate Enhancement Olefins">{{cite journal|last=Ito|first=Osamu|coauthors=Yuichi Arito, and Minoru Matsuda|title=Captodative Effects on Rate of Addition Reactions of Arylthiyl Radical to Disubstituted Olefins|journal=Journal of Chemical Society, Perkin Transaction II|year=1988|pages=869–873}}</ref> This is influenced by the substituent's ability to delocalize the radical ion in the [[Transition state theory|transition state structure]].<ref name="The Captodative Effect" /> Delocalizing the radical ion stabilizes the transition state structure. As a result, the energy of activation decreases, enhancing the rate of the overall reaction. 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.<ref name="Rate Enhancment Methylenecyclopropane">{{cite journal|last=Creary|first=Xavier|coauthors=M. E. Mehrisheikh-Mohammadi|title=Captodative Rate Enhancement in the Methylenecyclopropane Rearrangement|journal=The Journal of Organic Chemistry|year=1985|volume=51|pages=2664–2668}}</ref>
+Certain substituents are better at stabilizing radical centers than others.<ref name="Rate Enhancement Olefins">{{cite journal|last1 = Ito|first1 = Osamu|first2 = Y.|last2 = Arito|first3 = M.|last3 = Matsuda|title=Captodative Effects on Rate of Addition Reactions of Arylthiyl Radical to Disubstituted Olefins|journal = [[Perkin Transactions|Journal of Chemical Society, Perkin Transaction 2]]|year = 1988|pages = 869–873|doi = 10.1039/P29880000869}}</ref> This is influenced by the substituent's ability to delocalize the radical ion in the [[Transition state theory|transition state structure]].<ref name="The Captodative Effect" /> Delocalizing the radical ion stabilizes the transition state structure. As a result, the energy of activation decreases, enhancing the rate of the overall reaction. 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.<ref name="Rate Enhancment Methylenecyclopropane">{{cite journal|last1 = Creary|first1 = X.|first2 = M. E.|last2 = Mehrisheikh-Mohammadi|title = Captodative Rate Enhancement in the Methylenecyclopropane Rearrangement|journal = [[Journal of Organic Chemistry]]|year = 1985|volume = 51|issue = 14|pages = 2664–2668|doi = 10.1021/jo00364a009}}</ref>
-Osamu Ito (et al.) observed the rate of addition reactions of arylthiyl radical to disubstituted olefins.<ref name="Rate Enhancement Olefins" /> The Olefin contained an EWG, a cyan group and varying EDGs. The authors observed how the varying EDGs effect the rate of the addition reactions.
+Ito and co-workers observed the rate of addition reactions of arylthiyl radical to disubstituted olefins.<ref name="Rate Enhancement Olefins" /> The olefins contained an EWG, a cyan group and varying EDGs. The authors observed how the varying EDGs effect the rate of the addition reactions.
 [[File:General Reaction Scheme.png|thumb|400px|center|General schematic of the addition reaction of arylthiyl radicals to captodative olefins.]]
-The rate of the addition reaction was accelerated by the following EDGs in increasing order: H< CH<sub>3</sub> <OCH<sub>2</sub>CH<sub>3</sub>. When R=OCH<sub>2</sub>CH<sub>3</sub>, the rate of the reaction is the fastest because the reaction has the smallest energy of activation (ΔG‡). The -OCH<sub>2</sub>CH<sub>3</sub> and the cyano group are able to delocalize the radical ion in the transition, 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. The hydrogen atom is not able to delocalize the radical ion. Thus, the reaction is slow relative to when R=OCH<sub>2</sub>CH<sub>3</sub>. When R=CH<sub>3</sub>, the rate of the reaction is faster relative to when R=H because methyl groups have more electron donating capability.<ref name="Rate Enhancement Olefins" /> However,  when the reaction rate is slower relative to when R=OCH<sub>2</sub>CH<sub>3</sub> because the radical ion is not delocalized the methyl group groups. Thus, the captodative does not influence the reaction rate if the radical ion is not delocalized onto both the EWG and EDG substituents.
+The rate of the addition reaction was accelerated by the following EDGs in increasing order: H < CH<sub>3</sub> < OCH<sub>2</sub>CH<sub>3</sub>. When R=OCH<sub>2</sub>CH<sub>3</sub>, the rate of the reaction is the fastest because the reaction has the smallest energy of activation (ΔG<sup>‡</sup>). The -OCH<sub>2</sub>CH<sub>3</sub> and the cyano group are able to delocalize the radical ion in the transition, 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. The hydrogen atom is not able to delocalize the radical ion. Thus, the reaction is slow relative to when R = OCH<sub>2</sub>CH<sub>3</sub>. When R = CH<sub>3</sub>, the rate of the reaction is faster relative to when R = H because methyl groups have more electron donating capability.<ref name="Rate Enhancement Olefins" /> However, when the reaction rate is slower relative to when R = OCH<sub>2</sub>CH<sub>3</sub> because the radical ion is not delocalized the methyl group groups. Thus, the captodative does not influence the reaction rate if the radical ion is not delocalized onto both the EWG and EDG substituents.
 [[File:New Transition State.png|thumb|700px|center|Various electron-donating groups (shown in red) can affect the rate of the addition reactions of arythiyl radicals to captodative olefins]]
@@ Line 21: / Line 21: @@
 :[[File:2plus2 cyclodimerisation and intramolecular cyclisation of captodative olefins.jpg]]
-Similar effects have been discussed for other cycloadditions such as [3+2], [4+2], and [3+4] for captodative ethylenes.<ref name="Friedel Craft">{{cite journal|last=Herrera|first=Rafael|coauthors=Hugo A. Jimenez-Vazquez, Franciso Delgado, Bijorn C.G. Soderberg, and Joaquin Tamariz|title=1-Acetyvinyl Acrylates: New Captodative Olefins Bearing and Internal Probe for the Evaluation of the Relative Reactivity of Captodative against Electron-Deficient Double Bond in Diels-Alders and Friedel-Crafts Reaction|journal=Journal of the Brazilian Chemical Society|year=2005|volume=16|issue=3A|pages=456–466}}</ref>  Effects have also been reported in cases like [[Diels-Alder]] and [[Friedel-Crafts]] reactions in cases where nucleophilic olefins react inefficiently, attributed to the transition state being close to a biradical and thus stabilized.<ref name = "Stella" /><ref>{{cite journal|last=Stella|first=L|coauthors=Boucher|title=Capto-dative substituent effects. 121 - New ketene equivalents for diels-alder cycloadditions|journal=Tetrahedron Letters|year=1982|volume=22|issue=9|pages=953–956}}</ref>  These studies have revealed a direct dependence on Δω, difference in electrophilicity, and the polar nature of the reaction. They have been used because of their highly reactive, stereoselective, regioselective nature within these reactions.<ref name="Friedel Craft" /><ref>{{cite journal|last=Domingo|first=Luis|journal=Journal of Organic Chemistry|year=2008|month=March|issue=73|pages=4615–4624|doi=10.1021/jo800572a}}</ref>
+Similar effects have been discussed for other cycloadditions such as [3+2], [4+2], and [3+4] for captodative ethylenes.<ref name="Friedel Craft">{{cite journal|last1 = Herrera|first1 = R.|first2 = H. A.|last2 = Jimenez-Vazquez|first3 = F.|last3 = Delgado|first4 = B. C. G.|last4 = Soderberg|first5 = J.|last5 = Tamariz|title = 1-Acetyvinyl Acrylates: New Captodative Olefins Bearing and Internal Probe for the Evaluation of the Relative Reactivity of Captodative against Electron-Deficient Double Bond in Diels-Alders and Friedel-Crafts Reaction|journal = [[Journal of the Brazilian Chemical Society]]|year = 2005|volume = 16|issue = 3A|pages = 456–466|doi = 10.1590/S0103-50532005000300021}}</ref>  Effects have also been reported in cases like [[Diels-Alder]] and [[Friedel-Crafts]] reactions in cases where nucleophilic olefins react inefficiently, attributed to the transition state being close to a biradical and thus stabilized.<ref name = "Stella" /><ref>{{cite journal|last1 = Stella|first1 = L.|last2 = Boucher|first2 = J.-L.|title = Capto-dative Substituent Effects. 12<sup>1</sup> - New Ketene Equivalents for Diels-Alder Cycloadditions|journal = [[Tetrahedron Letters]]|year = 1982|volume = 22|issue = 9|pages = 953–956|doi = 10.1016/S0040-4039(00)86992-0}}</ref>  These studies have revealed a direct dependence on Δω, difference in electrophilicity, and the polar nature of the reaction. They have been used because of their highly reactive, stereoselective, regioselective nature within these reactions.<ref name="Friedel Craft" /><ref>{{cite journal|last1 = Domingo|first1 = L.|first2 =  E.|last2 = Chamorro|first3 = P.|last3 = Pérez|title = Understanding the Reactivity of Captodative Ethylenes in Polar Cycloaddition Reactions. A Theoretical Study|journal = [[Journal of Organic Chemistry]]|year = 2008|volume = 73|issue = 12|pages = 4615–4624|doi = 10.1021/jo800572a}}</ref>
 :[[File:Diels Alder.png|500px]]
 :[[File:Friedel Craft Reaction.png|500px]]
-Captodative olefins in reactions also show interfering effects with the typical [[kinetic isotope effect]], allowing atypical reactions to occur with isotope-labeled molecules<ref>{{cite journal|last=Wood|first=Mark|title=Synthetic use of primary kinetic isotope effect in hydrogen atom transfer 2: generation of captodatively stabilised radicals|journal=Organic and Biomolecular Chemistry|year=2013|month=March|issue=11|page=2712|doi=10.1039/c3ob4027Sd}}</ref> and demonstrating that the mechanisms and transition states of these reactions has been influenced.
+Captodative olefins in reactions also show interfering effects with the typical [[kinetic isotope effect]], allowing atypical reactions to occur with isotope-labeled molecules<ref>{{cite journal|last1 = Wood|first1 = M.|first2 = S.|last2 = Bissiriou|first3 = C.|last3 = Lowe|first4 = K. M.|last4 = Windeatt|title = Synthetic Use of the Primary Kinetic Isotope Effect in Hydrogen Atom Transfer 2: Generation of Captodatively Stabilised Radicals|journal = [[Organic and Biomolecular Chemistry]]|year = 2013|volume = 11|page = 2712|doi = 10.1039/C3OB40275D}}</ref> and demonstrating that the mechanisms and transition states of these reactions has been influenced.
 ==Polymer science application==
-[[Free radical polymerization]], where radicals are the chain carriers in the propagation of the process, accounted for 40 billion of the 110 billion pounds of polymers produced in the United States in 2001.<ref>{{cite book|last = Odian|first = G.|title = Principles of Polymerization|publisher = Wiley-Interscience|location = New York|year = 2004|edition = 4th|isbn = 9780471274001}}</ref> Captodative olefins have a specific advantage of being responsive to solvent effects without the effect of destabilizing the radical. They have also shown to undergo their radical transformation spontaneously which allows them to be useful in polymerization mechanism elucidation and better understood through [[Nuclear magnetic resonance spectroscopy|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.
+[[Free radical polymerization]], where radicals are the chain carriers in the propagation of the process, accounted for 40 billion of the 110 billion pounds of polymers produced in the United States in 2001.<ref>{{cite book|last = Odian|first = G.|title = Principles of Polymerization|publisher = Wiley-Interscience|location = New York|year = 2004|edition = 4th|isbn = 9780471274001}}</ref> Captodative olefins have a specific advantage of being responsive to solvent effects without the effect of destabilizing the radical.<ref name = "Tanaka" /> They have also shown to undergo their radical transformation spontaneously which allows them to be useful in polymerization mechanism elucidation and better understood through [[Nuclear magnetic resonance spectroscopy|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.
 [[File:Solvent Affinity effects of substituents.jpg|thumb|500px|right|Substituents on the monomer can affect solvent affinities]]
 [[File:Polar effect.jpg|thumb|400px|right|How a captodative monomer can form a polar polymer]]
@@ Line 38: / Line 38: @@
 # [[Bifunctional]] polymers, with two different functional groups at every monomer unit, are commonly formed from the captodative monomers.
 ## Dative groups substantially alter the solubility through [[Intermolecular force|Hydrogen bonding]] in specific bifunctional polymers( see figure above). However no clear correlation has been developed at this time, since not all combinations of substituents and solubilities have been investigated.
-# Captodative polymer is highly functional in chelates with certain metals.<ref>{{cite journal|last=Tanaka|first=Hitoshi|journal=Progress in Polymer Science|year=2003|pages=1171–1203|doi=10.1016/S0079-6700(03)00013-3}}</ref>
+# Captodative polymer is highly functional in chelates with certain metals.<ref name "Tanaka">{{cite journal|last = Tanaka|first = H.|journal = [[Progress in Polymer Science]]|title = Captodative Modification in Polymer Science|year = 2003|volume = 28|issue = 7|pages = 1171–1203|doi = 10.1016/S0079-6700(03)00013-3}}</ref>
 ==References==