scholarly journals Copolymerization of CO2 and epoxides mediated by zinc organyls

RSC Advances ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 3673-3679 ◽  
Author(s):  
Christoph Wulf ◽  
Ulrike Doering ◽  
Thomas Werner
Keyword(s):  
Cyclohexene Oxide ◽  
Reaction Parameters ◽  
Co Catalyst ◽  
Reaction Proceeds ◽  
Halogen Free

Simple zinc organyls (R2Zn) efficiently catalyze the copolymerization of CO2 and cyclohexene oxide. The effect of various reaction parameters has been studied. The reaction proceeds under halogen-free conditions and no co-catalyst is required.

scholarly journals Computational investigation of the control of the thermodynamics and microkinetics of the reductive amination reaction by solvent coordination and a co-catalyst

RSC Advances ◽  
2018 ◽  
Vol 8 (64) ◽  
pp. 36662-36674 ◽  
Author(s):  
Esra Boz ◽  
Nurcan Ş. Tüzün ◽  
Matthias Stein
Keyword(s):  
Tertiary Amine ◽  
Reductive Amination ◽  
Computational Investigation ◽  
Reaction Parameters ◽  
Co Catalyst ◽  
Amination Reaction ◽  
Green Production

Green production of tertiary amine from sustainable sources can be controlled by appropriate choice of reaction parameters identified by computational means.

scholarly journals DFT Study of Stereoselective Ketene-imine Cycloadditions, Evaluation of Possible Solvent Effects with IEF-PCM

2018 ◽  
Vol 62 (4) ◽  
Author(s):  
Balázs Komjáti ◽  
Bianka Szokol ◽  
Benjámin Kováts ◽  
Péter Kegye ◽  
József Nagy
Keyword(s):  
Experimental Data ◽  
Solvent Effects ◽  
Substituent Effects ◽  
Chiral Auxiliary ◽  
Electrostatic Repulsion ◽  
Chiral Auxiliaries ◽  
Reaction Parameters ◽  
Reaction Proceeds ◽  
Stereoselective Reactions ◽  
Main Factor

The formal [2+2] cycloaddition of ketenes and imines, also known as Staudinger synthesis, is a facile method for the synthesis of biologically important β-lactam derivatives. In this paper two previously reported stereoselective reactions were investigated with computational methods. Our computations support experimental data that a chiral imine, derived from d-glyceraldehyde reacting with ketenes, yields almost exclusively one out of the possible four diastereomers. The reaction proceeds stepwise, first addition of the imine to the ketene yields an intermediate, then the product is formed in a conrotatory electrocyclization. Results indicate that the electrostatic repulsion of the chiral auxiliary group is the main factor of the stereoselectivity, but solvent and substituent effects are not negligible. Calculations were performed at M06-2X/6-31+G** level of theory combined with IEF-PCM solvation, in common solvents such as toluene, THF, dichloromethane, acetonitrile and water. These results provide useful insight for the development of new chiral auxiliaries and optimizing reaction parameters.

Scandium(III) Triflate as a Lewis Acid Catalyst of Oxime Ligation

2020 ◽  
Vol 73 (4) ◽  
pp. 377
Author(s):  
Philip A. Cistrone ◽  
Anouk Dirksen ◽  
Sampat Ingale ◽  
Philip E. Dawson
Keyword(s):  
Lewis Acid ◽  
Functional Group ◽  
Acidic Solution ◽  
Acid Catalyst ◽  
Biological Applications ◽  
Co Catalyst ◽  
Reaction Proceeds ◽  
Order Of Magnitude ◽  
Aryl Amines ◽  
Lewis Acid Catalyst

Imine-forming reactions are widely applicable in bioconjugation owing to their high chemoselectivity. The ligation of a ketone or aldehyde with an aminooxy functional group to form a physiologically stable oxime bond is often used to link complex and precious biomolecules. Although the reaction proceeds modestly in acidic solution, the abundance of protonated carbonyl species at pH 7 limits its utility in many biological applications. The use of nucleophilic aryl amines, such as aniline or a phenylenediamine, allows a high population of protonated Schiff base to undergo transimination to the oxime product. Although this method affords significant enhancements at low pH, reactions can still be sluggish at neutral pH, especially with ketones such as acetophenone that are commonly used in bioconjugation. Here, we employ scandium(iii) trifluromethanesulfonate (triflate) (Sc(OTf)3), a uniquely water-stable Lewis acid, as a co-catalyst with ortho-phenylenediamine in the oxime ligation to yield up to an order of magnitude rate enhancement over the catalysts when applied individually.

scholarly journals Copolymerization of Phthalic Anhydride with Epoxides Catalyzed by Amine-bis(phenolate) Chromium(III) Complexes

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1785
Author(s):  
Wiktor Bukowski ◽  
Agnieszka Bukowska ◽  
Aleksandra Sobota ◽  
Maciej Pytel ◽  
Karol Bester
Keyword(s):  
Phthalic Anhydride ◽  
Styrene Oxide ◽  
Glycidyl Ether ◽  
Molar Ratio ◽  
Phenyl Glycidyl Ether ◽  
Cyclohexene Oxide ◽  
Catalytic Systems ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Organic Bases

The effect of ligand structure on the catalytic activity of amine-bis(phenolate) chromium(III) complexes in the ring-opening copolymerization of phthalic anhydride and a series epoxides was studied. Eight complexes differing in the donor-pendant group (R1) and substituents (R2) in phenolate units were examined as catalysts of the model reaction between phthalic anhydride and cyclohexane oxide in toluene. They were used individually or as a part of the binary catalytic systems with nucleophilic co-catalysts. The co-catalyst was selected from the following organic bases: PPh3, DMAP, 1-butylimidazole, or DBU. The binary catalytic systems turned out to be more active than the complexes used individually, and DMAP proved to be the best choice as a co-catalyst. When the molar ratio of [PA]:[epoxide]:[Cr]:[DMAP] = 250:250:1:1 was applied, the most active complex (R1-X = CH2NMe2, R2 = F) allowed to copolymerize phthalic anhydride with differently substituted epoxides (cyclohexene oxide, 4-vinylcyclohexene oxide, styrene oxide, phenyl glycidyl ether, propylene oxide, butylene oxide, and epichlorohydrin) within 240 min at 110 °C. The resulting polyesters were characterized by Mn up to 20.6 kg mol−1 and narrow dispersity, and they did not contain polyether units.

Alternating Ring-Opening Copolymerization of Cyclohexene Oxide and Maleic Anhydride with Diallyl-Modified Manganese(III)–Salen Catalysts

2016 ◽  
Vol 69 (1) ◽  
pp. 47 ◽  
Author(s):  
Dengfeng Liu ◽  
Zhao Zhang ◽  
Xingmei Zhang ◽  
Xingqiang Lü
Keyword(s):  
Maleic Anhydride ◽  
Ring Opening ◽  
Monomer Conversion ◽  
Catalytic Performance ◽  
Chain Growth ◽  
Cyclohexene Oxide ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Polymer Chain Growth ◽  
Catalytic Performances

A series of diallyl-modified (salen)MnIII complexes have been designed, synthesized, and applied in the cyclohexene oxide and maleic anhydride ring-opening copolymerization. The experimental results show that these complexes are effective in the presence of co-catalyst 4-(dimethylamino)pyridine (DMAP). Of all the five catalysts, the catalyst (salcyen)MnCl (salcyen = 2-((E)-(2-((E)-5-allyl-2-hydroxy-3-methoxybenzylideneamino)cyclohexylimino)methyl)-4-allyl-6-methoxyphenol) exhibited the best catalytic performance under the conditions applied, and the cyclohexane of diimine bridge is conjugated with the two diallyl-salen-type moieties. This conjugation can increase the electron density of the centre MnIII cation so that catalyst (salcyen)MnCl favours the formation of reaction intermediates. Moreover, the anion effect of Cl– is proved to be the best in the catalytic performances. Among the three co-catalysts (DMAP, triphenylphosphine (Ph3P), and tetra-n-butylammonium bromide (n-Bu4NBr)) tested, DMAP is the most efficient towards monomer conversion and polymer chain growth.

scholarly journals Hydrogenation of Adiponitrile to Hexamethylenediamine over Raney Ni and Co Catalysts

2020 ◽  
Vol 10 (21) ◽  
pp. 7506 ◽  
Author(s):  
Younghyun Lee ◽  
Sung Woo Lee ◽  
Hyung Ju Kim ◽  
Yong Tae Kim ◽  
Kun-Yi Andrew Lin ◽  
...  
Keyword(s):  
Metal Leaching ◽  
Catalyst Loading ◽  
Ni Catalyst ◽  
Reaction Parameters ◽  
Reaction Conditions ◽  
Co Catalyst ◽  
Co Catalysts ◽  
Raney Ni ◽  
Higher Temperature ◽  
Product Solution

Hexamethylenediamine (HMDA), a chemical for producing nylon, was produced on Raney Ni and Raney Co catalysts via the hydrogenation of adiponitrile (ADN). HMDA was hydrogenated from ADN via 6-aminohexanenitrile (AHN). For the two catalysts, the effects of five different reaction parameters (reaction temperature, H2 pressure, catalyst loading, and ADN/HMDA ratio in the reactant) on the hydrogenation of ADN were investigated. Similar general trends demonstrating the dependence of ADN hydrogenation on the reaction conditions for both catalysts were observed: higher temperature (60–80 °C) and H2 pressure, as well as lower ADN/catalyst and ADN/HMDA ratios, led to higher HMDA yields. A further increase in temperature from 80 to 100 °C increased the HMDA yield from 90.5 to 100% for the Raney Ni catalyst, but did not affect the HMDA yield (85~87%) for the Raney Co catalyst. A 100% HMDA yield (the highest yield reported to date) was also achieved via ADN hydrogenation over the Raney Ni catalyst, with a high HMDA content in the reactant (e.g., ADN/HMDA volumetric ratio of 0.06). No sign of metal leaching into the product solution was found, meaning that the Raney Ni and Raney Co catalysts were stable during ADN hydrogenation.

scholarly journals Efficient Production of Poly(Cyclohexene Carbonate) via ROCOP of Cyclohexene Oxide and CO2 Mediated by NNO-Scorpionate Zinc Complexes

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2148
Author(s):  
Sonia Sobrino ◽  
Marta Navarro ◽  
Juan Fernández-Baeza ◽  
Luis F. Sánchez-Barba ◽  
Agustín Lara-Sánchez ◽  
...  
Keyword(s):  
Ring Opening ◽  
Zinc Complexes ◽  
Efficient Production ◽  
Cyclohexene Oxide ◽  
X Ray Diffraction ◽  
Co Catalyst ◽  
X Ray ◽  
Mild Conditions ◽  
High Yields ◽  
Very High

New mono- and dinuclear chiral alkoxide/thioalkoxide NNO-scorpinate zinc complexes were easily synthesized in very high yields, and characterized by spectroscopic methods. X-ray diffraction analysis unambiguously confirmed the different nuclearity of the new complexes as well as the variety of coordination modes of the scorpionate ligands. Scorpionate zinc complexes 2, 4 and 6 were assessed as catalysts for polycarbonate production from epoxide and carbon dioxide with no need for a co-catalyst or activator under mild conditions. Interestingly, at 70 °C, 10 bar of CO2 pressure and 1 mol % of loading, the dinuclear thioaryloxide [Zn(bpzaepe)2{Zn(SAr)2}] (4) behaves as an efficient and selective one-component initiator for the synthesis of poly(cyclohexene carbonate) via ring-opening copolymerization of cyclohexene oxide (CHO) and CO2, affording polycarbonate materials with narrow dispersity values.

Observations of the Thermal Decomposition of Brucite

1968 ◽  
Vol 26 ◽  
pp. 446-447
Author(s):  
P. L. Burnett ◽  
W. R. Mitchell ◽  
C. L. Houck
Keyword(s):  
Thermal Decomposition ◽  
Magnesium Oxide ◽  
Basal Plane ◽  
Magnesium Ions ◽  
A Value ◽  
Reaction Proceeds

Natural Brucite (Mg(OH)2) decomposes on heating to form magnesium oxide (MgO) having its cubic ﹛110﹜ and ﹛111﹜ planes respectively parallel to the prism and basal planes of the hexagonal brucite lattice. Although the crystal-lographic relation between the parent brucite crystal and the resulting mag-nesium oxide crystallites is well known, the exact mechanism by which the reaction proceeds is still a matter of controversy. Goodman described the decomposition as an initial shrinkage in the brucite basal plane allowing magnesium ions to shift their original sites to the required magnesium oxide positions followed by a collapse of the planes along the original <0001> direction of the brucite crystal. He noted that the (110) diffraction spots of brucite immediately shifted to the positions required for the (220) reflections of magnesium oxide. Gordon observed separate diffraction spots for the (110) brucite and (220) magnesium oxide planes. The positions of the (110) and (100) brucite never changed but only diminished in intensity while the (220) planes of magnesium shifted from a value larger than the listed ASTM d spacing to the predicted value as the decomposition progressed.

THE X2BO and X2BS (X = HYDROGEN OR HALOGEN) FREE RADICALS

2014 ◽  
Author(s):  
Dennis Clouthier ◽  
Phillip Sheridan ◽  
Bing Jin ◽  
Robert Grimminger
Keyword(s):  
Free Radicals ◽  
Halogen Free

Solar photocatalysis mediated by ZnO for the removal of last traces of Indigo carmine dye pollutant from water

2018 ◽  
Vol 4 (02) ◽  
Author(s):  
Veena Vijayan ◽  
Suguna Yesodharan ◽  
E. P. Yesodharan
Keyword(s):  
Indigo Carmine ◽  
Parent Compound ◽  
Oxygen Demand ◽  
Green Technology ◽  
Solar Photocatalysis ◽  
Reaction Proceeds ◽  
Transient Intermediates ◽  
Significant Chemical ◽  
Hydroxyl Free Radicals ◽  
Purification Of Water

Solar photocatalysis as a potential green technology for the removal of traces of the dye pollutant Indigo carmine (IC) from water is investigated using ZnO as the catalyst. Degradation/decolorization alone does not result in complete decontamination as seen from the significant Chemical Oxygen Demand (COD) of water even after the parent compound has disappeared completely. The degradation proceeds through many intermediates which also get mineralized eventually but slowly. Oxalic acid is identified as a stable slow mineralizing degradation product which itself is formed from other transient intermediates. Effect of various parameters such as catalyst dosage, concentration of the dye, pH, temperature, presence of contaminant salts etc. on the degradation is investigated and quantified. Oxidants such as S2O82- and H2O2 have only moderate influence on the degradation. The degradation follows variable kinetics depending on the concentration of the substrate. The reaction proceeds very slowly in the absence of O2 indicating the importance of reactive oxygen species and hydroxyl free radicals in photocatalysis. H2O2 formed insitu in the system undergoes concurrent decomposition resulting in stabilization in its concentration. The study demonstrates that solar photocatalysis can be used as a viable tool for the purification of water contaminated with traces of IC.

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