scholarly journals Unique reactivity of B in B[Ge9Y3]3 (Y = H, CH3, BO, CN): formation of a Lewis base

2019 ◽  
Vol 21 (42) ◽  
pp. 23301-23304
Author(s):  
G. Naaresh Reddy ◽  
Rakesh Parida ◽  
R. Inostroza-Rivera ◽  
Arindam Chakraborty ◽  
Puru Jena ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Boron Compounds ◽  
Zintl Ion ◽  
Acid Nature ◽  
Boron Center

Boron compounds usually exhibit Lewis acidity at the boron center due to the presence of vacant p-orbitals. But using Zintl-ion based groups (Ge9Y3, Y = H, CH3, BO, CN), we can alter Lewis acid nature of B to a Lewis base.

Fluorinated 9-borafluorenes vs. conventional perfluoroaryl boranes — Comparative Lewis acidity

2005 ◽  
Vol 83 (12) ◽  
pp. 2098-2105 ◽  
Author(s):  
Preston A Chase ◽  
Patricio E Romero ◽  
Warren E Piers ◽  
Masood Parvez ◽  
Brian O Patrick
Keyword(s):  
Key Words ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Acid Strength ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Electrochemical Studies ◽  
Steric Factors

Perfluorinated 9-phenyl-9-borafluorene, 1, is an antiaromatic analog of the well-known tris(pentafluorophenyl)borane. Spectroscopic, structural, and electrochemical studies have been performed on 1 and its Lewis base adducts with MeCN, THF, and PMe3 with a view to assessing its comparative Lewis acid strength relative to B(C6F5)3. For the sterically undemanding Lewis base MeCN, 1 and B(C6F5)3 have comparable LA strengths, while for more sterically prominent THF, 1 is clearly the stronger Lewis acid (LA) based on competition experiments. We conclude that steric factors, rather than antiaromaticity, are the most important determinants in the LA strength differences between 1 and B(C6F5)3.Key words: boranes, Lewis acids, fluorinated compounds, heterocycles.

scholarly journals Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai
Keyword(s):  
Natural Rubber ◽  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Superior Performance ◽  
Lewis Acidity ◽  
Lewis Acid Sites ◽  
Niobium Oxides ◽  
Silica Nanocomposite ◽  
Loading Amount

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.

The structure and activity of potassium supported on SBA-15 molecular sieve: Density functional theory study

2014 ◽  
Vol 13 (01) ◽  
pp. 1350076 ◽  
Author(s):  
Bing Liu ◽  
Daxi Wang ◽  
Zhongxue Wang ◽  
Zhen Zhao ◽  
Yu Chen ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Lewis Acid ◽  
Molecular Sieve ◽  
Active Sites ◽  
Density Functional ◽  
Structural Model ◽  
Vibrational Frequencies ◽  
Oxygen Molecule ◽  
Lewis Base ◽  
Functional Theory

The geometries, vibrational frequencies, electronic properties and reactivity of potassium supported on SBA-15 have been theoretically investigated by the density functional theory (DFT) method. The structural model of the potassium supported on SBA-15 was constructed based on our previous work [Wang ZX, Wang DX, Zhao Z, Chen Y, Lan J, A DFT study of the structural units in SBA-15 mesoporous molecular sieve, Comput. Theor. Chem.963, 403, 2011]. This paper is the extension of our previous work. The most favored location of potassium atom was obtained by the calculation of substitution energy. The calculated vibrational frequencies of K /SBA-15 are in good agreement with the experimental results. By analyzing the properties of electronic structure, we found that the O atom of Si - O (2)- K group acts as the Lewis base center and the K atom acts as the Lewis acid center. The reactivity of K /SBA-15 was investigated by calculating the activation of oxygen molecule. The oxygen molecule can be activated by K /SBA-15 with an energy barrier of 103.2 kJ/mol. In the final state, the activated oxygen atoms become new Lewis acid centers, which are predicted to act as the active sites in the catalytic reactions. This study provides a deep insight into the properties of supported potassium catalysts and offers fundamental information for further research.

Erratum to “Synthesis and structure of potential Lewis acid–Lewis base bifunctional catalysts: 2-N,N-diisopropylaminobenzylboronate derivatives” [J. Organomet. Chem. 690 (2005) 4784–4793]

2006 ◽  
Vol 691 (3) ◽  
pp. 538
Author(s):  
Samuel W. Coghlan ◽  
Richard L. Giles ◽  
Judith A.K. Howard ◽  
Leonard G.F. Patrick ◽  
Michael R. Probert ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Bifunctional Catalysts

Lewis Base Mediated β-Elimination and Lewis Acid Mediated Insertion Reactions of Disilazido Zirconium Compounds

2013 ◽  
Vol 135 (40) ◽  
pp. 15225-15237 ◽  
Author(s):  
KaKing Yan ◽  
Juan J. Duchimaza Heredia ◽  
Arkady Ellern ◽  
Mark S. Gordon ◽  
Aaron D. Sadow
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Insertion Reactions ◽  
Zirconium Compounds

scholarly journals Lewis acid- and/or Lewis base-catalyzed [3+2] cycloaddition reaction: synthesis of pyrazoles and pyrazolines

2008 ◽  
Vol 49 (48) ◽  
pp. 6768-6772 ◽  
Author(s):  
Palakodety Radha Krishna ◽  
Empati Raja Sekhar ◽  
Florence Mongin
Keyword(s):  
Lewis Acid ◽  
Cycloaddition Reaction ◽  
Lewis Base ◽  
Reaction Synthesis

Empirical Lewis acid strengths for 135 cations bonded to oxygen

2017 ◽  
Vol 73 (5) ◽  
pp. 956-961 ◽  
Author(s):  
Olivier Charles Gagné ◽  
Frank Christopher Hawthorne
Keyword(s):  
Lewis Acid ◽  
Strong Correlation ◽  
Ionization Energy ◽  
Acid Strength ◽  
Lewis Base

New and updated Lewis acid strengths are listed for 135 cations bonded to oxygen for use with published Lewis base strengths. A strong correlation between Lewis acid strength and ionization energy is shown, and correlation with electronegativity is confirmed.

scholarly journals Lewis Base Activation of Lewis Acid: A Detailed Bond Analysis

ACS Omega ◽  
2018 ◽  
Vol 3 (11) ◽  
pp. 16292-16300 ◽  
Author(s):  
Gianluca Ciancaleoni
Keyword(s):  
Lewis Acid ◽  
Lewis Base

scholarly journals New insights into the Lewis acidity of guanidinium species: Lewis acid interaction provides reactivity

2020 ◽  
Vol 23 (2) ◽  
pp. 185-199
Author(s):  
Muhammad Ageel Ashraf ◽  
Cheng Li ◽  
Fataneh Norouzi ◽  
Dangquan Zhang
Keyword(s):  
Lewis Acid ◽  
Lewis Acidity ◽  
Acid Interaction
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