Mechanistic Insights into the Organopolymerization of N-Methyl N-Carboxyanhydrides Mediated by N-Heterocyclic Carbenes

Handle URI:
http://hdl.handle.net/10754/622427
Title:
Mechanistic Insights into the Organopolymerization of N-Methyl N-Carboxyanhydrides Mediated by N-Heterocyclic Carbenes
Authors:
Falivene, Laura ( 0000-0003-1509-6191 ) ; Al-Ghamdi, Miasser ( 0000-0002-7192-4660 ) ; Cavallo, Luigi ( 0000-0002-1398-338X )
Abstract:
We report on a DFT investigation of initiation, propagation, and termination in the organopolymerization of N-methyl N-carboxyanhydrides toward cyclic poly(N-substituted glycine)s, promoted by N-heterocyclic carbenes (NHC). Calculations support the experimentally based hypothesis of two competing initiation pathways. The first leading to formation of a zwitterionic adduct by nucleophilic addition of the NHC to one of the carbonyl groups of monomer. The second via acid–base reactivity, starting with the NHC promoted abstraction of a proton from the methylene group of the monomer, leading to an ion-pair-type adduct, followed by nucleophilic attack of the adduct to a new monomer molecule. Chain elongation can proceed from both the initiation adducts via nucleophilic attack of the carbamate chain-end to a new monomer molecule via concerted elimination of CO2 from the carbamate chain-end. Energy barriers along all the considered termination pathways are remarkably higher that the energy barrier along the chain elongation pathways, consistent with the quasi-living experimental behavior. Analysis of the competing termination pathways suggests that the cyclic species determined via MALDI-TOF MS experiments consists of a zwitterionic species deriving from nucleophilic attack of the N atom of the carbamate chain-end to the C═O group bound to the NHC moiety.
KAUST Department:
KAUST Catalysis Center (KCC); Physical Sciences and Engineering (PSE) Division
Citation:
Falivene L, Al Ghamdi M, Cavallo L (2016) Mechanistic Insights into the Organopolymerization of N-Methyl N-Carboxyanhydrides Mediated by N-Heterocyclic Carbenes. Macromolecules 49: 7777–7784. Available: http://dx.doi.org/10.1021/acs.macromol.6b01722.
Publisher:
American Chemical Society (ACS)
Journal:
Macromolecules
Issue Date:
4-Oct-2016
DOI:
10.1021/acs.macromol.6b01722
Type:
Article
ISSN:
0024-9297; 1520-5835
Sponsors:
This work was supported by funding from King Abdullah University of Science and Technology (KAUST).
Additional Links:
http://pubs.acs.org/doi/abs/10.1021/acs.macromol.6b01722
Appears in Collections:
Articles; Physical Sciences and Engineering (PSE) Division; KAUST Catalysis Center (KCC)

Full metadata record

DC FieldValue Language
dc.contributor.authorFalivene, Lauraen
dc.contributor.authorAl-Ghamdi, Miasseren
dc.contributor.authorCavallo, Luigien
dc.date.accessioned2017-01-02T09:28:30Z-
dc.date.available2017-01-02T09:28:30Z-
dc.date.issued2016-10-04en
dc.identifier.citationFalivene L, Al Ghamdi M, Cavallo L (2016) Mechanistic Insights into the Organopolymerization of N-Methyl N-Carboxyanhydrides Mediated by N-Heterocyclic Carbenes. Macromolecules 49: 7777–7784. Available: http://dx.doi.org/10.1021/acs.macromol.6b01722.en
dc.identifier.issn0024-9297en
dc.identifier.issn1520-5835en
dc.identifier.doi10.1021/acs.macromol.6b01722en
dc.identifier.urihttp://hdl.handle.net/10754/622427-
dc.description.abstractWe report on a DFT investigation of initiation, propagation, and termination in the organopolymerization of N-methyl N-carboxyanhydrides toward cyclic poly(N-substituted glycine)s, promoted by N-heterocyclic carbenes (NHC). Calculations support the experimentally based hypothesis of two competing initiation pathways. The first leading to formation of a zwitterionic adduct by nucleophilic addition of the NHC to one of the carbonyl groups of monomer. The second via acid–base reactivity, starting with the NHC promoted abstraction of a proton from the methylene group of the monomer, leading to an ion-pair-type adduct, followed by nucleophilic attack of the adduct to a new monomer molecule. Chain elongation can proceed from both the initiation adducts via nucleophilic attack of the carbamate chain-end to a new monomer molecule via concerted elimination of CO2 from the carbamate chain-end. Energy barriers along all the considered termination pathways are remarkably higher that the energy barrier along the chain elongation pathways, consistent with the quasi-living experimental behavior. Analysis of the competing termination pathways suggests that the cyclic species determined via MALDI-TOF MS experiments consists of a zwitterionic species deriving from nucleophilic attack of the N atom of the carbamate chain-end to the C═O group bound to the NHC moiety.en
dc.description.sponsorshipThis work was supported by funding from King Abdullah University of Science and Technology (KAUST).en
dc.publisherAmerican Chemical Society (ACS)en
dc.relation.urlhttp://pubs.acs.org/doi/abs/10.1021/acs.macromol.6b01722en
dc.titleMechanistic Insights into the Organopolymerization of N-Methyl N-Carboxyanhydrides Mediated by N-Heterocyclic Carbenesen
dc.typeArticleen
dc.contributor.departmentKAUST Catalysis Center (KCC)en
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalMacromoleculesen
kaust.authorFalivene, Lauraen
kaust.authorAl-Ghamdi, Miasseren
kaust.authorCavallo, Luigien
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