scholarly journals Preparation of Butadiene-Isoprene Copolymer with High Vinyl Contents by Al(OPhCH3)(i-Bu)2/MoO2Cl2∙TNPP

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 527 ◽  
Author(s):  
Peipei Li ◽  
Kai Liu ◽  
Zhe Fu ◽  
Yongliang Yu ◽  
Zhaobo Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Monomer Conversion ◽  
Experimental Results ◽  
Reactivity Ratios ◽  
Constant Ratio ◽  
Active Centers ◽  
Coordination Polymerization ◽  
Co Catalyst ◽  
Phenyl Phosphate

In this study, a butadiene-isoprene coordination polymerization was initiated by a binary molybdenum (Mo)-based catalytic system consisting of modified MoO2Cl2 as the primary catalyst, triethyl aluminum substituted by m-cresol as the co-catalyst and tris(nonyl phenyl) phosphate (TNPP) as the ligand. The effects of the amount of catalyst and type of co-catalyst were investigated in detail. Experimental results indicated that when the butadiene-isoprene coordination polymerization was initiated by the binary Mo-based catalytic system, the monomer conversion could reach 90%. The resulting butadiene units were primarily based on 1,2-structures, and the reactivity ratios of butadiene and isoprene were 1.13 and 0.31, respectively. The reaction in the catalytic system was attributed to the non-ideal and non-constant ratio copolymerization. When the addition of isoprene monomers was relatively low, the isoprene units on the butadiene-isoprene copolymers were primarily based on the 1,2- and 3,4-structures. Moreover, the orientation of active centers to 1,2- and 3,4-structures gradually decreased with an increase in the addition of isoprene monomers, which resulted in the generation of high vinyl butadiene-isoprene copolymers.

Thermoregulated Aqueous Biphasic Catalysis of Sonogashira Reactions

2015 ◽  
Vol 68 (10) ◽  
pp. 1614 ◽  
Author(s):  
Xiaohua Zhao ◽  
Xiang Liu ◽  
Ming Lu
Keyword(s):  
Catalytic System ◽  
Catalytic Reaction ◽  
High Efficiency ◽  
The Novel ◽  
Biphasic Catalysis ◽  
Co Catalyst ◽  
Highly Efficient ◽  
Water Based ◽  
Aqueous Biphasic ◽  
Sonogashira Reactions

A water-based thermoregulated system for Pd-catalyzed Sonogashira reactions is presented, which allows for not only a highly efficient homogeneous catalytic reaction, but also an easy separation/recovery of the catalyst. The novel catalytic system exhibits high efficiency and excellent reusability. In addition, the Sonogashira reactions are performed with Pd(OAc)2 without a copper co-catalyst.

Ethene/Propene Copolymerization with High Product of Reactivity Ratios from a Single Center, Metallocene-Based Catalytic System

1998 ◽  
Vol 31 (11) ◽  
pp. 3409-3416 ◽  
Author(s):  
Maurizio Galimberti ◽  
Fabrizio Piemontesi ◽  
Ofelia Fusco ◽  
Isabella Camurati ◽  
Mara Destro
Keyword(s):  
Catalytic System ◽  
Reactivity Ratios ◽  
Single Center

scholarly journals Dual Catalytic Enantioselective Desymmetrization of Allene-Tethered Cyclohexanones

2020 ◽  
Author(s):  
Lin Zhang ◽  
Ken Yamazaki ◽  
Jamie Leitch ◽  
Ruben Manzano ◽  
Victoria Atkinson ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Catalytic System ◽  
Density Functional ◽  
Functional Theory ◽  
Co Catalyst ◽  
Mechanistic Pathway

<p>The construction of enantioenriched azabicyclo[3.3.1]nonan-6-one heterocycles via an enantioselective desymmetrization of allene-linked cyclohexanones, enabled through a dual catalytic system, that provides synchronous activation of the cyclohexanone with a chiral prolinamide and the allene with a copper(I) co-catalyst to deliver the stereodefined bicyclic core, is described. Successful application to oxygen analogues was also achieved, thereby providing a new enantioselective synthetic entry to architecturally complex bicyclic ethereal frameworks. The mechanistic pathway and the origin of enantio- and diastereoselectivities has been uncovered using density functional theory (DFT) calculations.</p>

scholarly journals Enantiodivergent Non-Linear Effects in Asymmetric Catalysis

2020 ◽  
Author(s):  
Yannick Geiger ◽  
thierry achard ◽  
aline maisse-françois ◽  
Stephane Bellemin-Laponnaz
Keyword(s):  
Metal Complexes ◽  
Asymmetric Catalysis ◽  
Catalytic System ◽  
Catalyst Concentration ◽  
Enantiomeric Excess ◽  
Product Formation ◽  
Experimental Results ◽  
Non Linear ◽  
Linear Effects ◽  
Special Case

In this paper, we theoretically discuss the enantiodivergent product formation in asymmetric catalysis, a process in which the sign of the overall product enantiomer switches upon a change of catalyst concentration. The presented model is based on a catalytic system that consists of both discrete and dimeric aggregated metal complexes, in competition and in equilibrium. These concepts were then expanded to a non-enantiopure catalyst, giving rise to enantiodivergent non-linear effects – a special case of a hyperpositive non-linear effects where the product enantiomer’s sign switches upon a change of the catalyst enantiomeric excess. Different cases are considered allowing a discussion of the influence of the parameters governing both models. Finally, we present experimental results that support the enantiodivergence while varying the concentration of enantiopure catalyst or while varying the enantiomeric excess of the catalyst, using chiral N-methylephedrine as a ligand for the enantioselective addition of dimethylzinc to benzaldehyde.

scholarly journals Cobalt-Mediated Radical Copolymerization of Vinylidene Fluoride and 2,3,3,3-Trifluoroprop-1-ene

Polymers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2676
Author(s):  
Panagiotis G. Falireas ◽  
Bruno Ameduri
Keyword(s):  
Diblock Copolymers ◽  
Molar Mass ◽  
Vinylidene Fluoride ◽  
Monomer Conversion ◽  
Radical Copolymerization ◽  
Reactivity Ratios ◽  
Mean Square ◽  
Kinetics Studies ◽  
Lower Reactivity ◽  
Fitting Model

New copolymers based on vinylidene fluoride (VDF) and 2,3,3,3-tetrafluoroprop-1-ene (1234yf) were synthesized by organometallic-mediated radical copolymerization (OMRcP) using the combination of bis(tert-butylcyclohexyl) peroxydicarbonate initiator and bis(acetylacetonato)cobalt(II), (Co(acac)2) as a controlling agent. Kinetics studies of the copolymerization of the fluoroalkenes copolymers were monitored by GPC and 19F NMR with molar masses up to 12,200 g/mol and dispersities (Đ) ranging from 1.33 to 1.47. Such an OMRcP behaves as a controlled copolymerization, evidenced by the molar mass of the resulting copolymer-monomer conversion linear relationship. The reactivity ratios, ri, of both comonomers were determined by using the Fineman-Ross and Kelen-Tüdos fitting model leading to rVDF = 0.384 ± 0.013 and r1234yf = 2.147 ± 0.129 at 60 °C, showing that a lower reactivity of VDF integrated in the copolymer to a greater extent leads to the production of gradient or pseudo-diblock copolymers. In addition, the Q (0.03) and e (0.06 and 0.94) parameters were assessed, as well as the dyad statistic distributions and mean square sequence lengths of PVDF and P1234yf.

Binary molybdenum-based catalyst for coordination polymerization of styrene

2016 ◽  
Vol 49 (5) ◽  
pp. 408-421 ◽  
Author(s):  
Jieting Geng ◽  
Youguo Shao ◽  
Feng Song ◽  
Feng Li ◽  
Jing Hua
Keyword(s):  
Molecular Weight ◽  
Catalyst Activity ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Catalyst System ◽  
Bulk Polymerization ◽  
Molar Ratio ◽  
Scanning Calorimetry ◽  
Coordination Polymerization ◽  
Co Catalyst

Coordination polymerization of styrene (St) using molybdenum pentachloride supported by phosphite ligand in the presence of metal organic compound was studied for the first time. The types of phosphite and co-catalysts significantly affected the catalytic activity of the molybdenum (V) (Mo(V)) active center and the number-average molecular weight ( Mn) of the resultant polymer. Among the examined catalysts, tri(nonylphenyl)phosphite (TNPP) ligand and AlOPhCH3( i-Bu)2 as co-catalyst provided the polymer with highest yield (up to 87.1%), metallocene as co-catalyst provided the polymer with highest Mn (up to 5.32 × 105). The effect of [P]/[Mo] molar ratio on catalyst activity of the polymerization was discussed and the structures of Mo·TNPP complexes were preliminarily studied by infrared (IR) and ultraviolet spectroscopies. Besides, the polystyrene (PS) samples synthesized through bulk polymerization and solution polymerization were characterized by gel permeation chromatography, IR, carbon 13 nuclear magnetic resonance, and differential scanning calorimetry, respectively, and the results indicated both of the PS had high molecular weight (approximately 105) and atactic structure. All these results demonstrated that Mo(V) catalyst system was very effective for St polymerization.

Catalytic Destruction and Removal of Toluene by Microwave/Fe3O4 System

2008 ◽  
Vol 47-50 ◽  
pp. 335-338 ◽  
Author(s):  
Kai Yuan Cheng ◽  
Chen Yu Chang ◽  
Yung Hsu Hsieh ◽  
Kuo Shan Yao ◽  
Ta Chih Cheng ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Catalytic System ◽  
Thermal Destruction ◽  
New Technology ◽  
Packed Column ◽  
Reaction Chamber ◽  
Microwave Oven ◽  
Experimental Results ◽  
Catalytic Destruction ◽  
Volatile Organic

A microwave/Fe3O4 catalytic system was proposed for treatment of volatile organic carbons (VOCs). This system comprises a household microwave oven modified as the reaction chamber, which was fitted with a vertical, cylindrical quartz reactor comprising a catalytic packed column filled with granular Fe3O4, a microwave catalyst of iron (II, III) oxide. Experimental results showed that the destruction and removal efficiency (DRE) of toluene by microwave alone was close to zero, but with the microwave/Fe3O4 system, the temperature of the catalytic packed column increased rapidly and reached thermal balance within 10-15 min. Analysis of the rear gas after combustion showed that most of the toluene was thermal oxidized into CO2 and H2O. The successful application of the proposed microwave/Fe3O4 system to thermal destruction of toluene promises a new technology for treatment of VOCs.

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