diels-alder reaction teacher : prof. guey-sheng liou advisor : prof. ching-i huang speaker :...

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Diels-Alder Reaction

Teacher : Prof. Guey-Sheng Liou

Advisor : Prof. Ching-I Huang

Speaker : Wei-Ting Li

Date : 2014.1.3

N. Yoshie, Encyclopedia of Polymer Science and Technology. Diels-Alder Polymers: 1-18 (2013)

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Outline• Diels-Alder Reaction

• Diels-Alder Polymerization

• Furan and Maleimide

• Anthracene and Maleimide

• Functions of Diels-Alder Polymer

• Reversibility

• Healing Polymers

• Conclusion

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Kurt Alder1902~1958GermanyNobel Prize in Chemistry (1950)

Otto Diels1876~1954GermanyNobel Prize in Chemistry (1950)

Diels, O. .; Alder, K. . (1928). "Synthesen in der hydroaromatischen Reihe". Justus Liebig's Annalen der Chemie 460: 98–122.

[4+2] Cycloaddition

Retro Diels-Alder Reaction

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Diels, O. .; Alder, K. . (1928). "Synthesen in der hydroaromatischen Reihe". Justus Liebig's Annalen der Chemie 460: 98–122.

• Via a one-step, cyclic transition state, with no intermidiates generated.

• Converts two pi bonds into two sigma bonds.

• Good control over regio- and stereochemical properties.

• Favor spontaneous at low temperature.

ΔH < 0

ΔS < 0

ΔG = ΔH – TΔS < 0

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Mechanism

L.G. Wade, Jr. Organic Chemistry

Electron

donating

groups

Electron withdrawi

nggroups

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Examples


Electron

donating

groups

Electron withdrawi

nggroups

Electron

donating

groups

Electron withdrawi

nggroups

Electron withdrawi

nggroups

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Orbital Symmetry


Symmetry-allowed

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Stereochemical Requirements of the Transition State


Syn addition

s-cis of the diene

The endo rule

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s-cis Conformation of the Diene


Cyclopentadiene is fixed in the s-cis

conformation, it is highly reactive.

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Syn Stereochemistry


trans

trans

trans

cis

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The Endo Rule


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Unsymmetrical Reagents


1,4-product

1,2-product

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• Reversibility


• Conclusion

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Diels-Alder Polymerization

• Representative diene-dienophile combinations for polymer synthesis



• Cyclopentadiene

• Dithioester and Dienes

• Researchers have focused on the diene-dienophile combination.

• Ease of reactant preparation.

• Reaction rate.

• Equilibrium constant at room temperature.

• Temperaure above which the retro Diels-Alder reaction.


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Furan and Maleimide

• Extensively used in synthesizing functional polymers owing to its thermoreversibility.

• Although the relatively low thermal stability, reversibility at moderate temperature makes the reaction very attractive as a source of a dynamic bond.

• General concern for environmental sustainability has stimulated much research toward green chemistry, including production of polymers from renewable resources.

A. Gandini, Prog. Polym. Sci. 38, 1–29 (2013).

Aromatization

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Furan and Maleimide


Linear Polymerization

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Furan and Maleimide


Non-linear Polymerizatio

n Dendrimer

NetworkPolymer

s

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Furan and Maleimide


Cross-linking

80℃

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Anthracene and Maleimide

• Thermally more stable than the furan/maleimide Diels-Alder adduct.

• The thermal stability also results in a higher rate of the cycloaddition.

• Simple reaction conditions, high yield, and high selectivity, make the reaction valuable in polymer synthesis.

• More often used in click reactions because of the thermal stability of the resultant products.


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H. Durmaz, A. Sanyal, G. Hizal, and U. Tunca, Polym. Chem. 3, 825–835 (2012).

ABC-type linear terpolymer

Three-arm star block

copolymer

Multiarm star terpolymer

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H. Durmaz, A. Sanyal, G. Hizal, and U. Tunca, Polym. Chem. 3, 825–835 (2012).

Heterograftterpolymer

H-shaped quintopolyme

r

Cyclic block copolymer

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B. Gacal, H. Durmaz, M. A. Tasdelen, G. Hizal, U. Tunca, Y. Yagci, and A. L. Demirel, Macromolecules 39, 5330–5336 (2006).

Graft

Dendronized

M. Tonga, N. Cengiz, M. M. Kose, T. Dede, and A. Sanyal, J. Polym. Sci., Part A: Polym. Chem. 48, 410–416 (2010).

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• Reversibility


• Conclusion

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Reversibility

• The thermoreversibility for Diels-Alder polymers to function as smart materials.

• Repeatable bonding/debonding in Diels-Alder polymers confers stimuli-responsive properties to gels, organic-inorganic hybrids, and core-cross-linked micelles, and provides a route to surface modification.

• Reworkability and recyclability of thermosets, adhesives, and foams.

• The Diels-Alder network polymers has been applied to lithiography.

• Nanoporous films were successfully fabricated by combining microphase separation in block copolymers and retro Diels-Alder reaction.


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Healing Polymers


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• Reversibility


• Conclusion

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Conclusion• Some Diels-Alder reactions are thermally reversible. Enthalpically favorable forward

cycloaddition proceeds at a low temperature, whereas the opposite cycloreversion proceeds at a moderate to high temperature.

• Recently, the Diels-Alder reaction has been rerecognized as a member of the click-chemistry family. Because of the simple reaction condition, high yield, and high selectivity.

• The Diels-Alder reaction is extensively used in polymer chemistry. Linear, network, and hyperbranched polymers as well as polymers with unique architectures have been prepared from monomers and prepolymers containing a diene and a dienophile.

• Diels-Alder click chemistry is a powerful tool for synthesizing polymers with various advanced architectures (e.g., block and graft copolymers, star polymers, telechelic polymers, dendrimers, and dendronized polymers).


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Thanks for your attention.

diels-alder reaction teacher : prof. guey-sheng liou advisor : prof. ching-i huang speaker :...

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