scholarly journals Mechanistic Insight into the Ring-Opening Polymerization of ɛ-Caprolactone and L-Lactide Using Ketiminate-Ligated Aluminum Catalysts

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1530 ◽  
Author(s):  
Lin ◽  
Jheng
Keyword(s):  
Thermal Effects ◽  
Ring Opening ◽  
Density Functional ◽  
Bond Cleavage ◽  
Ring Opening Polymerization ◽  
Catalyst Design ◽  
Reaction Conditions ◽  
Functional Theory ◽  
Cleavage Step ◽  
Insight Into

The reactivity and the reaction conditions of the ring-opening polymerization of ɛ-caprolactone (ɛ-CL) and L-lactide (LA) initiated by aluminum ketiminate complexes have been shown differently. Herein, we account for the observation by studying the mechanisms on the basis of density functional theory (DFT) calculations. The calculations show that the ring-opening polymerization of ɛ-CL and LA are rate-determined by the benzoxide insertion and the C–O bond cleavage step, respectively. Theoretical computations suggest that the reaction temperature of L–LA polymerization should be higher than that of ɛ-CL one, in agreement with the experimental data. To provide a reasonable interpretation of the experimental results and to give an insight into the catalyst design, the influence of the electronic, steric, and thermal effects on the polymerization behaviors will be also discussed in this study.

A Density Functional Theory Study on the Ring-Opening Polymerization of D-Lactide Catalyzed by a Bifunctional-Thiourea Catalyst

2009 ◽  
Vol 62 (2) ◽  
pp. 157 ◽  
Author(s):  
Rong-Xiu Zhu ◽  
Ruo-Xi Wang ◽  
Dong-Ju Zhang ◽  
Cheng-Bu Liu
Keyword(s):  
Density Functional Theory ◽  
Ring Opening ◽  
Density Functional ◽  
Population Analysis ◽  
Density Functional Theory Calculations ◽  
Ring Opening Polymerization ◽  
Acyl Transfer ◽  
Frontier Molecular Orbital ◽  
Functional Theory ◽  
Elimination Pathway

The thiourea-catalyzed methanolysis of d-lactide, a model system for the initiation and propagation of the organocatalyzed ring-opening polymerization (ROP) of lactide, has been studied by performing density functional theory calculations. Both the catalyzed and uncatalyzed reactions are explored along two possible pathways: one involves the stepwise addition–elimination pathway and the other is related to the concerted pathway. It is found that the reaction without the presence of the catalyst is difficult because the barrier involved is as high as 176 kJ mol–1. With the aid of a thiourea catalyst, the barrier is reduced to 88 kJ mol–1 with a preference for the stepwise addition–elimination mechanism over the concerted one. The role of the catalyst has been rationalized by analyzing the frontier molecular orbital interactions between the catalyst and substrates and by performing natural population analysis. Finally, another mechanism involving acyl transfer is discussed for the thiourea-catalyzed ROP.

scholarly journals Rationalizing the Reactivity of Mixed Allyl Rare-Earth Borohydride Complexes with DFT Studies

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 820
Author(s):  
Sami Fadlallah ◽  
Jashvini Jothieswaran ◽  
Iker Del Rosal ◽  
Laurent Maron ◽  
Fanny Bonnet ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Rare Earth ◽  
Ring Opening ◽  
Density Functional ◽  
Ring Opening Polymerization ◽  
Polymerization Reaction ◽  
Experimental Investigations ◽  
Dft Studies ◽  
Functional Theory ◽  
Activation Barriers

The reactivity of rare-earth complexes RE(BH4)2(C3H5)(THF)x (RE = La, Nd, Sm, Y, Sc) toward the Ring-Opening Polymerization (ROP) of ε-caprolactone (ε-CL) was rationalized by Density Functional Theory (DFT) calculations. Even if the polymerization reaction can be initiated by both RE-(BH4) and RE-allyl bonds, experimental investigations have shown that the initiation via the borohydride ligand was favored, as no allyl group could be detected at the chain-end of the resulting polymers. DFT studies could confirm these observations, as it was highlighted that even if the activation barriers are both accessible, the allyl group is not active for the ROP of ε-CL due to the formation of a highly stable intermediate that disfavors the subsequent ring-opening.

DFT Studies Provide Mechanistic Insight into Nickel-Catalyzed Cross-Coupling Involving Organoaluminum-Mediated C–O Bond Cleavage

Synlett ◽  
2017 ◽  
Vol 28 (19) ◽  
pp. 2565-2568 ◽  
Author(s):  
Chao Wang ◽  
Masanobu Uchiyama ◽  
Ze-Kun Yang
Keyword(s):  
Density Functional ◽  
Reaction Pathway ◽  
Bond Cleavage ◽  
Cross Coupling ◽  
Reductive Elimination ◽  
Lewis Acidity ◽  
Functional Theory ◽  
Mechanistic Insight ◽  
Insight Into ◽  
Strong Lewis Acidity

Density functional theory (DFT) calculations were performed to examine the reaction pathway of Ni-catalyzed cross-coupling with organoaluminum through C–O bond cleavage. The results indicate that the strong Lewis acidity of organoaluminums significantly facilitates the transmetalation step, but not the oxidative addition or reductive elimination step.

Mechanistic insight into the selective cyclization of arylnitrones to indolines via Rh(iii) catalyst: a theoretical study

RSC Advances ◽  
2016 ◽  
Vol 6 (28) ◽  
pp. 23265-23271 ◽  
Author(s):  
Tao Liu ◽  
Xiao-Wen Zheng ◽  
Ling-Li Han ◽  
Ya-Ping Li ◽  
Shu-Min Han ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Study ◽  
Coupling Reaction ◽  
Dft Study ◽  
Reaction Conditions ◽  
Functional Theory ◽  
Mechanistic Insight ◽  
Insight Into

A density functional theory (DFT) study was performed to understand detailed mechanisms for the Rh(iii)-catalyzed coupling reaction of phenylnitrone with diphenylacetylene in different reaction conditions.

scholarly journals C-C and C-H bond cleavage reactions in acenaphthylene aromatic molecule, an ab-initio density functional theory study

2019 ◽  
Vol 10 (4) ◽  
pp. 403-408 ◽  
Author(s):  
Muthana Abduljabbar Shanshal ◽  
Qhatan Adnan Yusuf
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Ring Opening ◽  
Density Functional ◽  
Bond Cleavage ◽  
Dft Method ◽  
Functional Theory ◽  
Ring Opening Reaction ◽  
Reaction Energies ◽  
Cleavage Reactions

The ab-initio DFT method (B3LYP) is applied to the study of the C-C and C-H bond cleavage reactions in acenaphthylene molecule. It is found that the C-C bond cleavage proceeds via a singlet aromatic transition state, compelled through a disrotatoric ring opening reaction. A sigmatropic H atom shift follows the transition state in some of these reactions, where the formation of a methylene -CH2,acetylenyl-, allenyl- or butadienyl moiety in the final product is possible. The calculated activation and reaction energies for the C-C ring opening are 164-236 and 52-193 kcal/mol, respectively. The calculated cleavage reaction energies for the C-H bonds are 117-122 kcal/mol and the activation energies are 147-164 kcal/mol.

scholarly journals Stability of oxidized states of ceria-supported PtOx particles under a wide range of gas-phase conditions

2021 ◽  
Author(s):  
Jon Eunan Quinlivan Domínguez ◽  
Konstantin Neyman ◽  
Albert Bruix
Keyword(s):  
Density Functional ◽  
Structural Complexity ◽  
Optimization Method ◽  
Catalyst Design ◽  
Oxidation States ◽  
Effect Of Temperature ◽  
Reaction Conditions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Wide Range

Nanostructured materials based on non-inert oxides CeO2 and PtyOx play a fundamental role in catalyst design. However, their characterization is often challenging due to their structural complexity and the tendency of the materials to change under reaction conditions. In this work, we combine calculations based on the density functional theory, a machine-learning assisted global optimization method (GOFEE) and ab initio thermodynamics to characterize stable oxidation states of ceria-supported PtyOx clusters in different environments. The collection of global minima for different stoichiometries resulting from the global optimisation effort is used to assess the effect of temperature, oxygen pressure, and support interactions on the phase diagrams, oxidation states, and structural properties of the PtyOx particles. We thus identify favoured structural motifs and O/Pt ratios, revealing that oxidized states of ceria-supported particles are more stable than reduced ones under a wide range of conditions. These results indicate that studies rationalizing activity of ceria-supported Pt clusters must consider such oxidized states, and that previous understanding of such materials obtained only with fully reduced Pt clusters may be incomplete.

scholarly journals Density functional theoretical studies on the ring-opening polymerization mechanism of oxetane cation series compounds

RSC Advances ◽  
2017 ◽  
Vol 7 (78) ◽  
pp. 49626-49632
Author(s):  
Hai-Xia Wang ◽  
Min Pu ◽  
Yu-Cheng Ding
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Ring Opening ◽  
Density Functional ◽  
Ring Opening Polymerization ◽  
Basis Set ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Polymerization Mechanism

The mechanism of ring-opening polymerization of oxetane cation series compounds was investigated using the B3LYP and MP2 methods of density functional theory andab initiomethods, at the basis set levels of 6-31G(d,p) and 6-311++G(d,p).

Sign in / Sign up

Export Citation Format

Share Document