DFT study on the [4+4] domino cycloaddition of ynones with benzylidenepyrazolones to access eight-membered cyclic ethers: effects of DBU vs. Et3N

2021 ◽  
Vol 45 (1) ◽  
pp. 131-140
Author(s):  
Binfang Yuan ◽  
Huimin Zhou ◽  
Youqing Yu ◽  
Xiaogang Guo ◽  
Yu Zhao ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Study ◽  
Cyclic Ethers ◽  
The Difference

The difference in the catalytic activity of bases is primarily attributed to their electron-donating ability (t-BuO− > DBU > Et3N).

Participation of 19-substituents in electrophilic additions to 6,7-unsaturated 5α-cholestane and B-homo 5α-cholestane derivatives; A case of competition between the participation of an ambident neighboring group and external nucleophile attack

1980 ◽  
Vol 45 (2) ◽  
pp. 559-583 ◽  
Author(s):  
Pavel Kočovský ◽  
Ladislav Kohout ◽  
Václav Černý
Keyword(s):  
Perchloric Acid ◽  
Hydrobromic Acid ◽  
Cyclic Ether ◽  
Cyclic Ethers ◽  
Neighboring Group ◽  
Acid Cleavage ◽  
Neighbouring Group Participation ◽  
Aqueous Perchloric Acid ◽  
The Difference ◽  
Electrophilic Additions

Hypobromous acid action upon the 6,7-unsaturated 19-substituted 5α-cholestans Va-Vc results in the formation of two types of products, the cyclic ethers IX as products of 5(O)n participation of the 19-substituent, and the bromohydrins X. All these compounds are formed from the 6α,7α-bromonium ions Va'-Vc'. Under the same conditions the B-homo-5α-cholestane derivatives VIIa-VIIc afforded solely the cyclic ethers XIV as products of 5(O)n participation of the 19-substituent in the cleavage of the bromonium ions VIIa'-VIIc'. Acid cleavage of the 6α,7α-epoxides VIb and VIc with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the cyclic ethers XI and the diols XII or bromohydrines XIII. The cyclic ethers XI arise by 5(O)n participation of the 19-substituent. The B-homo-6α, 7α-epoxide VIIIc on cleavage with aqueous perchloric acid have solely the cyclic ether XVc and by treatment with hydrobromic acid VIIIc afforded the mixture of XVc, as the main product, and of the bromohydrin XVIc. Discussed is the similarity of the bromonium ion cleavage with the fission of the corresponding epoxides, the mechanism of these reactions and the difference in the behaviour of the isomeric olefins Ia-c, IIIa-c, Va-c and VIIa-c and epoxides IIb,c, IVb,c, VIb,c and VIIIb,c. The competition between ambident neighbouring group participation and external nucleophile attack is discussed as well as the dependence of the products ratio on the nucleophilicity of the attacking species.

scholarly journals A diffusion anisotropy descriptor links morphology effects of H-ZSM-5 zeolites to their catalytic cracking performance

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiaoliang Liu ◽  
Jing Shi ◽  
Guang Yang ◽  
Jian Zhou ◽  
Chuanming Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Catalytic Cracking ◽  
Catalytic Performance ◽  
Zeolite Catalysts ◽  
Time Resolved ◽  
Cracking Performance ◽  
Morphology Effect ◽  
Ft Ir ◽  
The Difference ◽  
Dynamics Simulations

AbstractZeolite morphology is crucial in determining their catalytic activity, selectivity and stability, but quantitative descriptors of such a morphology effect are challenging to define. Here we introduce a descriptor that accounts for the morphology effect in the catalytic performances of H-ZSM-5 zeolite for C4 olefin catalytic cracking. A series of H-ZSM-5 zeolites with similar sheet-like morphology but different c-axis lengths were synthesized. We found that the catalytic activity and stability is improved in samples with longer c-axis. Combining time-resolved in-situ FT-IR spectroscopy with molecular dynamics simulations, we show that the difference in catalytic performance can be attributed to the anisotropy of the intracrystalline diffusive propensity of the olefins in different channels. Our descriptor offers mechanistic insight for the design of highly effective zeolite catalysts for olefin cracking.

Synthesis, structure, redox behavior, catalytic activity and DFT study of a new family of ruthenium(III)1-(arylazo)naphtholate complexes

2017 ◽  
Vol 830 ◽  
pp. 33-41 ◽  
Author(s):  
Madhan Ramesh ◽  
Mani Kalidass ◽  
Madhavan Jaccob ◽  
Dhananjayan Kaleeswaran ◽  
Galmari Venkatachalam
Keyword(s):  
Catalytic Activity ◽  
Dft Study ◽  
Redox Behavior ◽  
New Family

The Effect of Ni Precursor Salts on Diatomite Supported Ni-Mg Catalysts in Methanation of CO2

2021 ◽  
Vol 1016 ◽  
pp. 1417-1422
Author(s):  
Chao Sun ◽  
Jugoslav Krstic ◽  
Vojkan Radonjic ◽  
Miroslav Stankovic ◽  
Patrick da Costa
Keyword(s):  
Catalytic Activity ◽  
Atmospheric Pressure ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Nickel Salt ◽  
Nitrate Salt ◽  
Efficient Catalyst ◽  
Mild Conditions ◽  
The Difference ◽  
Supported Ni

This study is aimed to investigate the effect of Ni precursor salts on the properties (textural, phase-structural, reducibility, and basicity), and catalytic performance of diatomite supported Ni-Mg catalyst in methanation of CO2. The NiMg/D-X catalysts derived from various nickel salts (X = S-sulfamate, N-nitrate or A-acetate) were synthesized by the precipitation-deposition (PD) method. The catalysts were characterized by N2-physisorption, XRD, TPR-H2, and TPD-CO2 techniques. The different catalytic activity (conversion) and selectivity, observed in CO2 methanation carried out under relatively mild conditions (atmospheric pressure; temperatures: 250-450 °C) are related and explained by the difference in textural properties, metallic Ni-crystallite size, reducibility, and basicity of studied catalysts. The results showed that catalyst derived from Ni-nitrate salt (NiMg/D-N) is more suitable for the preparation of efficient catalyst for CO2 methanation than its counterparts derived from sulfamate (NiMg/D-S) or acetate (NiMg/D-A) nickel salt. The NiMg/D-N catalyst showed the highest specific surface area and total basicity, and the best catalytic performance with CO2 conversion of 63.3 % and CH4 selectivity of 80.9 % at 450 °C.

scholarly journals On the Catalytic Activity of [RuH 2 (PPh 3 ) 3 (CO)] (PPh 3 =triphenylphosphine) in Ruthenium‐Catalysed Generation of Hydrogen from Alcohols: a Combined Experimental and DFT study

ChemCatChem ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2995-3009
Author(s):  
Patrizia Lorusso ◽  
Shahbaz Ahmad ◽  
Karin Brill (née Schmid) ◽  
David J. Cole‐Hamilton ◽  
Nicolas Sieffert ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Study

Catalytic Activity of Titanium Silicalites—a DFT Study

1998 ◽  
Vol 175 (2) ◽  
pp. 170-174 ◽  
Author(s):  
Georgi N. Vayssilov ◽  
Rutger A. van Santen
Keyword(s):  
Catalytic Activity ◽  
Dft Study

A Study of Copper-Chromium Oxide Catalysts and a Method to Determine Catalytic Activities

1963 ◽  
Vol 7 ◽  
pp. 229-239
Author(s):  
M. Stammler ◽  
M. Pyzyna
Keyword(s):  
Catalytic Activity ◽  
Chromium Oxide ◽  
Oxide Catalysts ◽  
Linear Absorption ◽  
X Ray ◽  
Chromium Spinel ◽  
Copper Chromium ◽  
The Difference ◽  
Two Phases ◽  
Chromium Oxide Catalysts

AbstractAn extensive investigation of chemical composition, particle size, and surface area of copper-chromium oxide catalysts has been made. The two phases present in the activated material are copper oxide (CuO) and copper-chromium spinel (CuCr2O4). The crystallite size of the CuO phase (determined by X-ray diffraction line broadening) can be correlated with the catalytic activity measured on a CO-CO2 oxidation reaction. The catalytic activity of the oxide catalyst can be expressed as a function of the X-ray fluorescence intensity of the Cu Kα line even on changing the absolute copper concentration up to 3%. An attempt is made to explain this phenomenon by the heterogeneity effect caused by the difference in the linear absorption factors for the Cu Kα radiation in the system CuO-CuCr2O4.

Axial ligand effect on the catalytic activity of biomimetic Fe-porphyrin catalyst: An experimental and DFT study

2016 ◽  
Vol 344 ◽  
pp. 768-777 ◽  
Author(s):  
Konstantinos C. Christoforidis ◽  
Dimitrios A. Pantazis ◽  
Luis L. Bonilla ◽  
Eleni Bletsa ◽  
Maria Louloudi ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Axial Ligand ◽  
Dft Study ◽  
Ligand Effect
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