Mechanistic insights into the ring-opening of biomass derived lactones

Gupta, Shelaka; Arora, Rishabh; Sinha, Nishant K.; Alam, Md. Imteyaz; Haider, M. Ali

doi:10.1039/c5ra22832h

Cited by 30 publications

(25 citation statements)

References 55 publications

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“…It has been shown by several authors, through DFT analysis, that the reaction involves transition states exhibiting varying activation barriers . The initiation and propagation proceed via the most accessible pathway.…”

Section: Resultsmentioning

confidence: 99%

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

Munzeiwa

Nyamori

Omondi

2018

Applied Organom Chemis

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A series of Zn(II) and Cu(II) complexes were synthesized using unsymmetrical N,N′‐ diarylformamidine ligands, i.e. N‐(2‐methoxyphenyl)‐N′‐2,6‐dichorophenyl)‐formamidine (L1), N‐(2‐methoxyphenyl)‐N′‐phenyl)‐formamidine (L2), N‐(2‐methoxyphenyl)‐N′‐(2,6‐dimethylphenyl)‐formamidine (L3) and N‐(2‐methoxyphenyl)‐N′‐(2,6‐diisopropylphenyl)‐formamidine (L4). The complexes, [Zn2(L1)2(OAc)4] (1), [Zn2(L2)2(OAc)4] (2), [Zn2(L3)2(OAc)4] (3), [Zn2(L4)2(OAc)4] (4), [Cu2(L1)2(OAc)4] (5), [Cu2(L2)2(OAc)4] (6), [Cu2(L3)2(OAc)4] (7) and [Cu2(L4)2(OAc)4] (8), were prepared via a mechanochemical method with excellent yields between 95 ‐ 98% by reacting the metal acetates and corresponding ligands. Structural studies showed that both complexes are dimeric with a paddlewheel core structure in which the separation between the two metal centres are 2.9898 (8) and 2.6653 (7) Å in complexes 3 and 7, respectively. Complexes 1 – 8 were used in ring‐opening polymerization of ε‐caprolactone (ε‐CL) and rac‐lactide (rac‐LA). Zn(II) complexes were more active than Cu(II) complexes, with complex 1 bearing electron withdrawing chloro groups being the most active (kapp = 0.0803 h‐1). Low molecular weight poly‐(ε‐CL) and poly‐(rac‐LA) ranging from 1720 to 6042 g mol‐1, with broad molecular weight distribution (PDIs, 1.78 – 1.87) were obtained. Complex 2 gave reaction orders of 0.56 and 1.52 with respect to ε‐CL and rac‐LA, respectively.

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Section: Resultsmentioning

confidence: 99%

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

Munzeiwa

Nyamori

Omondi

2018

Applied Organom Chemis

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“…It is also highly significant that the reaction of the Brønsted acids with lactones-if we do not view the acid catalyst as a bifunctional agent-results in the formation of unsaturated carboxylic acids. Haider et al studied this issue in detail [179] at the GGA-PW91 [180] level of theory. The results of simulations demonstrates the linear correlation between the rate constants and the energies of the formation of oxocarbenium ions; these ions undergo nucleophilic attack of the water molecule not on carbonyl carbon, but on ω-carbon of the lactone ring, followed by dehydration (Scheme 11).…”

Section: Maron Et Al Computationally Studied the Catalytic Propertiementioning

confidence: 99%

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Nifant’ev

Ivchenko

2019

Polymers

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Organocatalysis is highly efficient in the ring-opening polymerization (ROP) of cyclic esters. A variety of initiators broaden the areas of organocatalysis in polymerization of different monomers, such as lactones, cyclic carbonates, lactides or gycolides, ethylene phosphates and phosphonates, and others. The mechanisms of organocatalytic ROP are at least as diverse as the mechanisms of coordination ROP; the study of these mechanisms is critical in ensuring the polymer compositions and architectures. The use of density functional theory (DFT) methods for comparative modeling and visualization of organocatalytic ROP pathways, in line with experimental proof of the structures of the reaction intermediates, make it possible to establish these mechanisms. In the present review, which continues and complements our recent manuscript that focused on DFT modeling of coordination ROP, we summarized the results of DFT modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification. 4 of 49 were found to be polymerizable due to strain in the ester group. In addition, the predominance of high-energy coiled conformations in linear homopolymers the formed from PDO, εCL and GL was proportionately less than extended conformations, in comparison to the inactive monomer γBL. However, while the prevalence of coiled conformations over extended conformations was expected for poly(LA), this factor does not affected the reactivity of lactides. Very good agreement between the experimental and calculated data for ROP of GL, l-LA and (R,S)-lactide [47] should be separately noted. 4-(Dimethylamino)pyridine (DMAP) and Related CompoundsDMAP was the first employed organocatalyst in polymer synthesis. In 2001, Nederberg et al. [48] reported the "first organocatalytic living polymerization" (Ð M < 1.2) of L-lactide (l-LA) mediated by DMAP or 4-pyrrolidinopyridine in the presence of ROH initiators. Four years later [49], Feng and Dong reported polymerization of ε-caprolactone (εCL) catalyzed by DMAP in the presence of chitozane as an initiator. Bourissou et al. studied the mechanism of DMAP-catalyzed ROP of l-LA and five-membered lactic O-carboxylic anhydride (lacOCA) [50]. Two possible reaction pathways were analyzed at the B3LYP/6-31G(d) level of theory [39,40,51]; the solvent effect of dichloromethane was taken into account through the PCM/SCRF model [52]. The modeled reaction was the methanolysis of l-LA or lacOCA; alternative nucleophilic/monomer (Scheme 1a) and basic/alcohol (Scheme 1b) activation mechanisms were proposed for these reactions, and then analyzed by DFT optimization of the key reaction intermediates and transition states, if necessary. Scheme 1. Schematic representation of the nucleophilic/monomer (a) and basic/alcohol (b) mechanisms for (Dimethylamino)pyridine (DMAP)-catalyzed methanolysis of l-LA. Author Contributions: Conceptualization, P.I.; Methodology, I.N. and P.I.; Writing-Original draft preparation, P.I.; Writing-Review and editing, I.N. and P.I.; V...

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“…[1][2][3][4][5] Some monomers such as 𝜖-caprolactone (𝜖-CL) and lactides (LAs), which are used for the synthesis of polyesters, such as poly(𝜖-caprolactone) and poly(lactic acid) (PLA), may be obtained from biobased biomasses by green processes. [6][7][8][9][10] These polyesters can be recycled, composted, and incinerated with low environmental impact. [7] The integration of bio-based monomer production with a biocatalytic polymerization process may afford a fully green, DOI: 10.1002/mren.202100044 biocatalytic route to bio-based polymers.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Modeling of Ring Opening Polymerization of Lactones under Microwave Irradiation

López‐Domínguez

Carranco‐Hernández

Vivaldo‐Lima

2021

Macro Reaction Engineering

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A kinetic study on the mathematical modeling of polymerization rate and molar mass development in the ring opening bulk polymerization (ROP) of lactones under microwave irradiation (MI), for the production of biodegradable green polymers used in the biomedical sector, is presented. Two modeling approaches, one based on calculation of average properties using a self‐developed code based on the method of moments, and the other one providing calculation of full molar mass distributions with the aid of the Predici software are contrasted. The observed enhancement on polymerization rate under MI is captured well by using a non‐thermal microwave effect modeling approach, namely, a microwave‐enhanced propagation model. The proposed approach is validated with available experimental data for ROP of ε‐caprolactone, a monomer which can be obtained from biomasses, using benzyl alcohol (BzOH) and stannous octoate (SnOc)2 as initiator and catalyst, respectively, at 150 °C. Seven case studies are analyzed, including ROPs carried out under both conventional heating (CH) and MI. The effect of initiator and alcohol initial concentrations on polymerization rate and molar mass distributions is analyzed. The advantages of using MI in ROP are assessed.

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Mechanistic insights into the ring-opening of biomass derived lactones

Abstract: Density functional theory calculations suggest the formation of an oxocarbenium ion intermediate in acid catalyzed ring-opening reactions of biomass derived lactones, which may play an important role in determining it's reactivity.

Cited by 30 publications

References 55 publications

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

Zn(II) and Cu(II) unsymmetrical formamidine complexes as effective initiators for ring‐opening polymerization of cyclic esters

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Kinetic Modeling of Ring Opening Polymerization of Lactones under Microwave Irradiation

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