Competition between cycloaddition and spontaneous copolymerization of 4-methyl-1,3-pentadiene with electrophilic olefins

Mikhael, Michael G.; Padías, Anne Buyle; Hall, H. K.

doi:10.1021/ma00074a002

Cited by 11 publications

(10 citation statements)

References 5 publications

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“…Both reactions proceed via second-order kinetics. Similar results were obtained from the investigations of the spontaneous reactions of 2-methyl-2,4-pentadiene (1,1-dimethylbuta-1,3diene) and of 1-methoxybuta-1,3-diene with electrophilic olefins, respectively [16] [17].…”

Section: Scheme 1 Tetramethylene Intermediates Initiating Spontaneousupporting

confidence: 84%

The Relationship of Cycloaddition Reactions to Spontaneous Vinyl Polymerizations

Hall

Padías

2005

Helvetica Chimica Acta

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To Professor Rolf Huisgen with grateful appreciation for his contributions to organic polymer chemistry! The zwitterionic ± biradical tetramethylene proposed by Huisgen as the key intermediate in stepwise [2 2] cycloaddition reactions has been shown to be the crucial intermediate in spontaneous vinyl polymerizations as well. Predominantly biradical tetramethylenes initiate free-radical copolymerizations, while predominantly zwitterionic tetramethylenes initiate cationic or anionic homopolymerizations. Stepwise cycloaddition is viewed as a spontaneous polymerization lacking a propagation step. These tendencies could be correlated in the form of an organic chemists Periodic Table, which has recently been put on a quantitative basis.Huisgen also showed experimentally that [4 2] Woodward ± Hoffman-allowed cycloadditions are completely concerted. Spontaneous copolymerizations accompanying these cycloadditions, therefore, were ascribed to the s-trans diene form. This concept was given support by kinetics studies, as well as by exclusive cycloaddition from s-cis cyclopentadiene, and exclusive copolymerization from s-trans verbenene.Introduction. ± The great poet builds larger than he knows. This familiar saying also applies to great scientists. When Rolf Huisgen was studying the role of the tetramethylene intermediate in [2 2] cycloaddition reactions, surely the idea that this intermediate might play an important role in polymer chemistry never crossed his mind. Yet this has proven to be the case.During the 1960s and 1970s, polymer chemists encountered various unexpected and perplexing observations in vinyl polymerizations. A tendency of the monomer units to alternate in the copolymer chain was observed. This was the case when electron-rich monomers, such as styrene or vinyl ethers, were copolymerized with electron-poor monomers, such as methyl acrylate or acrylonitrile. As the donor and acceptor character of the co-monomers increased, the alternation tendency grew stronger and stronger. Eventually, a new phenomenon set in, namely spontaneous polymerization. At first, spontaneous copolymerization occurred by a radical mechanism to form strictly alternating copolymers. With still stronger donor-substituted monomers, homopolymers of the donor monomer were found, which could only be formed by a spontaneous cationic homopolymerization.Attempts by polymer chemists to understand these phenomena centered on the visible charge-transfer (CT) complexes formed by the two monomers. It was attractive to suppose that free-radical homopolymerization of this CT complex would lead to the observed strictly alternating copolymers. But how this explained the cationic homopolymers or the CT complex initiated polymerizations, was not made clear.

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Section: Scheme 1 Tetramethylene Intermediates Initiating Spontaneousupporting

confidence: 84%

The Relationship of Cycloaddition Reactions to Spontaneous Vinyl Polymerizations

Hall

Padías

2005

Helvetica Chimica Acta

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“…The generality of this hypothesis was validated by extending these studies to other nucleophilic diene/electrophilic olefin combinations, which all led to mixtures of cycloadducts and copolymers: 1,1‐dimethylbutadiene with acrylonitrile, fumaronitrile, maleic anhydride, trimethyl ethylenetricarboxylate, dimethyl cyanofumarate, or methyl dicyanoacrylate 37. No solvent polarity effect on rates was seen, speaking for a P6 polar biradical.…”

Section: Introductionmentioning

confidence: 83%

A paradigm for the mechanisms and products of spontaneous polymerizations

Hall

Padías

2009

J. Polym. Sci. A Polym. Chem.

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“…In the case of weak donor and weak acceptor monomers (acrylonitrile:styrene system), i.e., very low electron disparity, no spontaneous reaction takes place. 1,16 On the basis of its Q-e values, 17 4-VP is considered to be a weakly electrophilic olefin. Therefore, 4-VP complexes with lithium salts and protic acids were prepared to increase its electrophilic character.…”

Section: Resultsmentioning

confidence: 99%

Effect of lithium perchlorate on the spontaneous copolymerization of 4-vinylpyridine with various electron-rich vinyl monomers

Choi¹,

Mikhael²,

Padías³

et al. 1999

J. Polym. Sci. A Polym. Chem.

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Competition between cycloaddition and spontaneous copolymerization of 4-methyl-1,3-pentadiene with electrophilic olefins

Cited by 11 publications

References 5 publications

The Relationship of Cycloaddition Reactions to Spontaneous Vinyl Polymerizations

The Relationship of Cycloaddition Reactions to Spontaneous Vinyl Polymerizations

A paradigm for the mechanisms and products of spontaneous polymerizations

Effect of lithium perchlorate on the spontaneous copolymerization of 4-vinylpyridine with various electron-rich vinyl monomers

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