A computational study of base-catalyzed reactions between isocyanates and epoxides affording 2-oxazolidones and isocyanurates

Okumoto, Satoshi; Yamabe, Shinichi

doi:10.1002/1096-987x(200102)22:3<316::aid-jcc1004>3.0.co;2-5

Cited by 22 publications

(20 citation statements)

References 14 publications

(12 reference statements)

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“…Okumoto et al 107 studied model reactions through ab initio calculations to determine the main reactions pathways (Scheme 20). The 2-oxazolidone 9 is thought to be produced by a dual S N2 reaction, where the catalyst (e.g., Cl − ) is a nucleophile and a leaving group on the ethylene−oxide carbon.…”

Section: Oxazolidonementioning

confidence: 99%

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

et al. 2012

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Section: Oxazolidonementioning

confidence: 99%

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

et al. 2012

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“…In the case of zwitterion 2, a new chemical shift at lower field would be expected however it was not observed. Previous research has reported a lower activation energy of 14.6 kcal/mol for zwitterion 1 and 34.3 kcal/mol for zwitterion 2, which further supports that zwitterion 1 is the true initiating species for the polymerization. For nucleophiles with varied nucleophilicity, the stronger ones lead to faster formation of the initiating species, resulting in significantly reduced gel time.…”

Section: Resultsmentioning

confidence: 88%

Isocyanurate transformation induced healing of isocyanurate–oxazolidone polymers

Zhang

Lin

Sodano

2019

J of Applied Polymer Sci

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Isocyanurate–oxazolidone (ISOX) polymers have been reported as a novel, intrinsically self‐healable thermoset, and their healing mechanism under the effect of nucleophiles, such as tertiary amines and pyridines during polymerization, is thoroughly investigated in this study. This work provides evidence that the healing behavior of the polymers results part from the transformation of isocyanurate to oxazolidone on the fracture surfaces of the ISOX polymers at elevated temperatures. The isocyanurate transformation is characterized by chemical composition of the ISOX polymers before and after a predetermined healing procedure, through a combination characterization of Fourier transform infrared spectroscopy and carbon nuclear magnetic resonance spectroscopy. From the chemical composition of the ISOX polymers, an increased oxazolidone fraction is observed after the healing event, which verifies the hypothesized healing mechanism. By correlating the change in oxazolidone fraction in the polymers during the healing event, with the corresponding healing performance of the polymers, healing efficiencies of the polymers are shown to be inversely proportional to the ratio of oxazolidone to isocyanurate in the polymers. The transformation to oxazolidone is also shown to be dependent on two variables, nucleophilicity of the polymerization catalyst and duration of the postcure. The isocyanate and epoxide polymerization mechanism in the presence of nucleophiles is also investigated to explain the effect of the catalyst nucleophilicity on the chemical composition as well as the healing performance of the ISOX polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48698.

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“…The mechanisms of these catalytic processes have been investigated using density functional theory (DFT) methods. 3,16,17,20,21,26 All the DFT results suggest that the isocyanate cyclotrimerization processes are highly exothermic, which demonstrates that isocyanurates are quite thermodynamically stabilized molecules.…”

Section: Introductionmentioning

confidence: 95%

Thermal stabilities and conformational behaviors of isocyanurates and cyclotrimerization energies of isocyanates: a computational study

et al. 2020

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Isocyanurates are cyclic trimers of isocyanate molecules. They are generally known as highly thermostable compounds. However, it is interesting how the thermal stabilities of the isocyanurate molecules will be altered depending on the substituents of their three nitrogen atoms. We performed computational investigations on the thermochemical behaviors of isocyanurate molecules with various alkyl and phenyl substituents. The cyclotrimerization processes of isocyanates are highly exothermic. Our best estimate of the enthalpy change for the cyclotrimerization of methyl isocyanate into trimethyl isocyanurate was À66.4 kcal mol À1 . Additional negative cyclotrimerization enthalpy changes were observed for n-alkylsubstituted isocyanates. This trend was enhanced with an extension of n-alkyl chains. Conversely, low negative cyclotrimerization enthalpy changes were shown for secondary and tertiary alkyl-substituted isocyanates. The n-alkyl-substituted isocyanurates were shown to be stabilized due to attractive dispersion interactions between the substituents. Meanwhile, the branched alkyl-substituted isocyanurates were destabilized due to the deformation of their isocyanurate rings. For various alkylsubstituted isocyanates, the sum of the deformation energy of the isocyanurate ring and the intramolecular inter-substituent nonbonding interaction energies was found to be linearly correlated with their cyclotrimerization energies. The cyclotrimerization energy for phenyl isocyanate was shown to have significantly deviated from the linear relationship observed for the alkyl-substituted isocyanurates. This is probably attributable to a remarkable change in the orbital resonance interactions during the cyclotrimerization of phenyl isocyanate to triphenyl isocyanurate.Scheme 1 Isocyanurate framework resulting from the cyclotrimerization of isocyanate molecules.15956 | RSC Adv., 2020, 10, 15955-15965This journal is a The energy value is provided in kcal mol À1 . The cyclotrimerization enthalpy at 298 K can be calculated by adding the enthalpy correction term to the electronic energy changes provided in the Table. The enthalpy correction terms are +5.1, +5.1, and +5.2 kcal mol À1 , respectively, for the B3LYP/ cc-pVTZ, B3LYP-GD3/cc-pVTZ, and MP2/cc-pVTZ optimized geometries. This journal isView Article Online a The intermolecular interaction energies were calculated with taking the corrections for the BSSEs into account. The calculated energy values are provided in kcal mol À1 . b The basis set cc-pVTZ was employed.This journal is

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A computational study of base-catalyzed reactions between isocyanates and epoxides affording 2-oxazolidones and isocyanurates

Cited by 22 publications

References 14 publications

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-isocyanate Polyurethane

Isocyanurate transformation induced healing of isocyanurate–oxazolidone polymers

Thermal stabilities and conformational behaviors of isocyanurates and cyclotrimerization energies of isocyanates: a computational study

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