scholarly journals Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate

2010 ◽  
Vol 6 ◽  
pp. 1043-1055 ◽  
Author(s):  
Michael North ◽  
Marta Omedes-Pujol
Keyword(s):  
Catalytic Activity ◽  
Propylene Carbonate ◽  
Lewis Base ◽  
Base Catalysis ◽  
Lewis Acidity ◽  
Mechanistic Study ◽  
Trimethylsilyl Cyanide ◽  
Trimethylsilyl Ethers ◽  
Rate Of Reaction ◽  
Cyanohydrin Synthesis

Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in propylene carbonate, indicating that in propylene carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from 51V NMR spectroscopy suggested that propylene carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane.

Investigation of Lewis Acid versus Lewis Base Catalysis in Asymmetric Cyanohydrin Synthesis

2010 ◽  
Vol 16 (37) ◽  
pp. 11367-11375 ◽  
Author(s):  
Michael North ◽  
Marta Omedes-Pujol ◽  
Courtney Williamson
Keyword(s):  
Lewis Acid ◽  
Lewis Base ◽  
Base Catalysis ◽  
Acid Versus ◽  
Cyanohydrin Synthesis

Isomerization ofn-butane on sulfated zirconia: Evidence for the dominant role of Lewis acidity on the catalytic activity

1994 ◽  
Vol 26 (3-4) ◽  
pp. 339-344 ◽  
Author(s):  
F. Pinna ◽  
M. Signoretto ◽  
G. Strukul ◽  
G. Cerrato ◽  
C. Morterra
Keyword(s):  
Catalytic Activity ◽  
Sulfated Zirconia ◽  
Dominant Role ◽  
Lewis Acidity

scholarly journals Kinetics and mechanism of meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate

2013 ◽  
Vol 15 (2) ◽  
pp. 107-111 ◽  
Author(s):  
D. Kungumathilagam ◽  
K. Karunakaran
Keyword(s):  
Acetic Acid ◽  
Catalytic Activity ◽  
Reaction System ◽  
Kinetic Scheme ◽  
Mechanistic Study ◽  
Radical Mechanism ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium ◽  
Catalysed Oxidation

Developing catalyst is very significant for biologically important reactions which yield products, used as drugs. Mechanistic study on meso-tetraphenylporphyriniron(III) chloride (TPP) catalysed oxidation of indole by sodium perborate in aqueous acetic acid medium have been carried out. The reaction follows a fractional order with respect to substrate and catalyst. The order with respect to oxidant was found to be one. Increase in the percentage of acetic acid and increase in the concentration of [H+] decreased the rate. The reaction fails to initiate polymerization, and a radical mechanism is ruled out. Activation and thermodynamic parameters have been computed. A suitable kinetic scheme based on these observations has been proposed. Significant catalytic activity is observed for the reaction system in the presence of TPP.

Tetracarboxyl-Functionalized Ionic Liquid: Synthesis and Catalytic Properties

2015 ◽  
Vol 68 (10) ◽  
pp. 1513 ◽  
Author(s):  
Miaona Feng ◽  
Guoying Zhao ◽  
Hongling Gao ◽  
Suojiang Zhang
Keyword(s):  
Ionic Liquid ◽  
Catalytic Activity ◽  
Ionic Liquids ◽  
Propionic Acid ◽  
Propylene Carbonate ◽  
Propylene Oxide ◽  
High Stability ◽  
Ammonium Acetate ◽  
Catalytic Properties ◽  
Potential Applications

Novel tetracarboxyl-functionalized 2,2′-biimidazolium-based ionic liquids (ILs) with different anions were synthesized in two steps from readily available and sustainable starting materials including ammonium acetate, glyoxal, and halogenated propionic acid. The functionalized IL exhibited higher catalytic activity towards the cycloaddition of CO2 to terminal epoxides. With propylene oxide as a substrate, the optimum yield of propylene carbonate reached 82.7 % at an initial CO2 pressure of 2.0 MPa for 4 h at 140°C. Moreover, the functionalized IL catalyst displayed a high stability and can be reused for at least five cycles without obvious loss of catalytic activity. The results provide a simple and economical way to synthesize multi-functionalized imidazolium-based ILs with versatile potential applications.

scholarly journals Dual metal and Lewis base catalysis approach for asymmetric synthesis of dihydroquinolines and the α-arylation of aldehydes via N-acyliminium ions

2015 ◽  
Vol 51 (87) ◽  
pp. 15788-15791 ◽  
Author(s):  
Chandra M. R. Volla ◽  
Eleonora Fava ◽  
Iuliana Atodiresei ◽  
Magnus Rueping
Keyword(s):  
Asymmetric Synthesis ◽  
Catalytic System ◽  
Optically Active ◽  
Lewis Base ◽  
Base Catalysis ◽  
Asymmetric Addition ◽  
Acyliminium Ions ◽  
Indium Triflate ◽  
Dual Metal

A dual catalytic system consisting of indium triflate and a chiral imidazolidinone catalyzes the asymmetric addition of aldehydes to N-acyl quinoliniums furnishing optically active dihydroquinolines in good yields and excellent selectivities.

Catalytic Activity of Cobalt Nanoparticles for Dye and 4-Nitro Phenol Degradation: A Kinetic and Mechanistic Study

2017 ◽  
Vol 49 (6) ◽  
pp. 438-454 ◽  
Author(s):  
Mohammad Naved Khan ◽  
Ommer Bashir ◽  
Tabrez Alam Khan ◽  
Shaeel Ahmed Al-Thabaiti ◽  
Zaheer Khan
Keyword(s):  
Catalytic Activity ◽  
Phenol Degradation ◽  
Cobalt Nanoparticles ◽  
Mechanistic Study

scholarly journals Mechanistic Study of the Electrosynthesis of Propylene Carbonate from Propylene Oxide and CO 2 on Copper Electrodes

2019 ◽  
Vol 6 (11) ◽  
pp. 2917-2923 ◽  
Author(s):  
Elena Pérez‐Gallent ◽  
Marta C. Figueiredo ◽  
Marc T. M. Koper
Keyword(s):  
Propylene Carbonate ◽  
Propylene Oxide ◽  
Mechanistic Study ◽  
Copper Electrodes

Evaluation of the Lewis acidity of metal complexes using ESI mass spectrometry

2020 ◽  
Vol 26 (5) ◽  
pp. 332-340
Author(s):  
Rong Zhang ◽  
Ping-Ping Li ◽  
Ge-Ge Gu ◽  
Wei-Min Ren
Keyword(s):  
Mass Spectrometry ◽  
Metal Complexes ◽  
Density Functional ◽  
Lewis Base ◽  
Lewis Acidity ◽  
Ionization Mass ◽  
Base Pairs ◽  
Esi Ms ◽  
Tetradentate Schiff Base ◽  
Schiff Base Metal Complexes

Metal complexes have extensive applications in catalysis, however, the efficient evaluation of Lewis acidity of metal complexes is still a challenge. Herein, we report a method by using electrospray ionization mass spectrometry (ESI-MS) to evaluate the Lewis acidity of metal complexes in the presence of a reference Lewis base, in which the value of the Lewis acidity can be quantized by the bond dissociation energy (BDE) of the resultant Lewis acid-base pairs. Using this method, the Lewis acidity of tetradentate Schiff-base metal complexes (designated as salenMX), a class of common metal complexes in the homogeneous catalysis, was studied in detail. For the salenM(III)X complexes (M = Al, Cr, Fe, Co), the Lewis acidity tendency is Al > Cr > Fe > Co due to a strong affinity between the Al complex and the reference Lewis base while a weak affinity concerning on the Co complex. Additionally, the effect of ligand steric and electronic nature on the Lewis acidity was studied by using Co complex. Furthermore, density functional theory (DFT) was employed to calculate the BDE, which consists with the results obtained from ESI-MS. The ESI-MS method provides a convenient and efficient method for evaluating the Lewis acidity of metal complexes.

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