Ionic Liquid Promoted Regio- and Stereo-Selective Thiolysis of Epoxides—A Simple and Green Approach to β-Hydroxy- and β-Keto Sulfides

2007 ◽  
Vol 60 (4) ◽  
pp. 278 ◽  
Author(s):  
Brindaban C. Ranu ◽  
Tanmay Mandal ◽  
Subhash Banerjee ◽  
Suvendu S. Dey
Keyword(s):  
Ionic Liquid ◽  
Organic Solvent ◽  
The Other ◽  
Green Approach ◽  
Other Hand ◽  
Basic Ionic Liquid ◽  
Epoxy Ketones ◽  
Stereo Selectivity

A variety of epoxides underwent facile cleavage by thiols under the catalysis of 1-methyl-3-butylimidazolium bromide, [bmIm]Br, to produce the corresponding β-hydroxy sulfides with high regio- and stereo-selectivity. On the other hand, a specially designed basic ionic liquid, [bmIm]OH, efficiently catalyzes the thiolysis of α,β-epoxy ketones providing β-keto sulfides through simultaneous retro-aldol cleavages. The reactions are clean, high yielding, and do not require any organic solvent. The catalyst is also recycled.

scholarly journals Highly Active Iminopyridyl Iron-Based Catalysts for the Polymerization of Isoprene

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3024 ◽  
Author(s):  
Obaid H. Hashmi ◽  
Yohan Champouret ◽  
Marc Visseaux
Keyword(s):  
Low Temperature ◽  
Electronic Properties ◽  
The Other ◽  
Co Catalysts ◽  
Highly Active ◽  
Other Hand ◽  
Iron Based ◽  
Stereo Selectivity ◽  
Iron Based Catalysts

A series of iminopyridyl-based ligands, 6-[(Ar)N=C(R)]-2-C6H5N [(Ar = 2,6-Me2-C6H3, R = Me (L1); Ar = 2,6-iPr2-C6H3, R = Me (L2); Ar = 2,6-Me2-C6H3, R = H (L3); Ar = 2,6-iPr2-C6H3, R = H (L4); Ar = 3,5-(CF3)2-C6H3, R = Me (L5); Ar = C6F5, R = Me (L6)], and their corresponding iron (II) complexes were developed to investigate their application in the controlled coordinative polymerization of isoprene. The modulation of steric and electronic properties within this family of ligands/pre-catalysts has shown to influence the stereo-selectivity and activity of the polymerization of isoprene after activation. Upon activation with various co-catalysts such as AliBu3/[Ph3C][B(C6F5)4], AlEt3/[Ph3C][B(C6F5)4] or MAO, the resulting catalysts produced polyisoprenes with an excellent conversion (>99% of 500–5000 equiv.) within less than 1 h (TOF > 500 h−1) and having a variety of stereo-/regio-regularities. The presence of electron-donating and withdrawing groups drastically impacted the activity and the stereoselectivity of the catalysts during the course of the polymerization of isoprene. When activated with AliBu3/[Ph3C][B(C6F5)4], the complexes {6-[(2,6-Me2-C6H3)N=C(Me)]-2-C6H5N}FeCl2 (C1) and {6-[(2,6-iPr2-C6H3)N=C(Me)]-2-C6H5N}FeCl2 (C2) exhibited moderate trans-1,4 selectivity (>67%) while the iron-based systems bearing related aldiminopyridyl ligands {6-[(2,6-Me2-C6H3)N=C(H)]-2-C6H5N}FeCl2 (C3) and {6-[(2,6-iPr2-C6H3)N=C(H)]-2-C6H5N}FeCl2 (C4) were found to afford significant cis-1,4 selectivity at low temperature (>86% at −40 °C). On the other hand, the ternary {6-[(3,5-(CF3)2-C6H3)N=C(Me)]-2-C6H5N}FeCl2 (C5) or {6-[(C6F5)N=C(Me)]-2-C6H5N}FeCl2 (C6)/AliBu3/[Ph3C][B(C6F5)4] catalytic combinations showed exceptional activity for the polymerization of isoprene (TOF > 1,000,000 h−1), albeit providing less stereoselectivity.

Effects of Organic Solvent Treated on the Performance and Structure of Polysulfone Tubular Ultrafiltration Membrane

2012 ◽  
Vol 164 ◽  
pp. 203-206 ◽  
Author(s):  
En Hua Liu ◽  
He Ying Xu ◽  
Xu Chen Zhao
Keyword(s):  
Organic Solvent ◽  
Organic Solvents ◽  
Water Flux ◽  
Ultrafiltration Membrane ◽  
The Other ◽  
Egg Protein ◽  
Other Hand

The paper studied the effect of different kinds of organic solvents treated polysulfone tubular ultrafiltration membrane on its performances and structure. The results show that the surface of membrane treaded with n-hexane are smoother and less hydrophily, the content of carbon element increased at the same time. On the other hand, the water flux of membrane treated with alkane decrease, but the rejections to MgSO4 and egg protein increase. While the surface of membrane treated with ethanol are rougher and more hydrophily, the contents of carbon and oxygen increase too. The water flux of membrane treated with alcohols increase obviously, but the rejection to egg protein decrease slightly.

scholarly journals Polymerization of Ethylene in the Presence of Various Ligand Organometallic Catalytic Systems

2020 ◽  
pp. 31-40
Author(s):  
Qanbarli Zeynab ◽  
Khanmetov Akber ◽  
Azizbeyli Hemide ◽  
Khamiyev Matlab
Keyword(s):  
Ionic Liquid ◽  
Ethylene Polymerization ◽  
The Other ◽  
Polymerization Process ◽  
Catalytic Systems ◽  
Zirconium Complexes ◽  
Other Hand ◽  
Physicochemical Methods ◽  
Liquid Type

This work presents the results on the preparation of new readily available zirconium-containing arylimine complex catalytic systems and their application together with metallocenes in ethylene polymerization. For this purpose, zirconium complexes with grafted ionic liquid type ligands were synthesized and tested in the ethylene polymerization process. On the other hand, it is known that one of the main industrial catalysts for the polymerization process of ethylene is dicycopentadienyl titanium and zirconium dichloride. Therefore, one of the main objectives of the work is to test the using of the newly synthesized complexes with the industrial Cp2TiCl2 catalyst. The products obtained were identified by various physicochemical methods and it was found that these catalytic systems allow one to control the structure and composition of the products obtained.

“Naked” S2O72– ions – the serendipitous formation of the disulfates [HPy]2[S2O7] and [bmim][HPy][S2O7] (HPy = pyridinium; bmim = 1-Butyl-3-methylimidazolium)

2015 ◽  
Vol 70 (1) ◽  
pp. 3-8
Author(s):  
Jörn Bruns ◽  
Christian Logemann ◽  
Alexander Weiz ◽  
Claudia Kolb ◽  
Mathias S. Wickleder
Keyword(s):  
Crystal Structure ◽  
Ionic Liquid ◽  
Charge Compensation ◽  
The Other ◽  
Side Product ◽  
Other Hand

Abstract[bmim][HPy][S2O7] [monoclinic, P21/n, Z = 4, a = 825.78(2), b = 1545.30(3), c = 1410.80(3) pm, β = 104.726(1)°, V = 1741.16(7) Å3] was obtained as a side product in the reaction of GeCl4, oleum (65% SO3), and the pyridine (Py) complex Py·SO3 in the ionic liquid 1-butyl-3-methylimidazolium hydrogensulfate, [bmim][HSO4], at 50 °C. Charge compensation of the disulfate ion is achieved by the counterions pyridinium, [HPy]+, and 1-butyl-3-methylimidazolium, [bmim]+. The crystal structure shows alternating layers of [bmim]+ cations on one hand and [HPy]+ cations and disulfate anions on the other hand. Pyridinium disulfate, [HPy]2[S2O7] [orthorhombic, P212121, Z = 4, a = 801.35(1), b = 1257.62(2), c = 1357.22(3) pm, V = 1367.80(4) Å3] was formed unexpectedly in the reaction of Eu2O3 and Py·SO3 in pyridine. The crystal structure exhibits a layer-like arrangement of disulfate and pyridinium moieties in the ab plane. In both compounds, the disulfate groups are essentially uncoordinated allowing for a detailed inspection of “naked” S2O72– ions.

A study of cometary eruptions through OH radio-lines

1999 ◽  
Vol 173 ◽  
pp. 249-254
Author(s):  
A.M. Silva ◽  
R.D. Miró
Keyword(s):  
Short Duration ◽  
Growth Curves ◽  
The Other ◽  
Initial Mass ◽  
Radio Lines ◽  
Other Hand ◽  
Sudden Rise

AbstractWe have developed a model for theH2OandOHevolution in a comet outburst, assuming that together with the gas, a distribution of icy grains is ejected. With an initial mass of icy grains of 108kg released, theH2OandOHproductions are increased up to a factor two, and the growth curves change drastically in the first two days. The model is applied to eruptions detected in theOHradio monitorings and fits well with the slow variations in the flux. On the other hand, several events of short duration appear, consisting of a sudden rise ofOHflux, followed by a sudden decay on the second day. These apparent short bursts are frequently found as precursors of a more durable eruption. We suggest that both of them are part of a unique eruption, and that the sudden decay is due to collisions that de-excite theOHmaser, when it reaches the Cometopause region located at 1.35 × 105kmfrom the nucleus.

Closing the GAP—A 5Å Scanning Microscope

1969 ◽  
Vol 27 ◽  
pp. 6-7
Author(s):  
A. V. Crewe
Keyword(s):  
Normal Form ◽  
The Other ◽  
Resolving Power ◽  
Scanning Microscope ◽  
Conventional Microscope ◽  
Other Hand ◽  
Closing The Gap ◽  
Thermal Sources ◽  
Better Than ◽  
Transmission Microscope

We have become accustomed to differentiating between the scanning microscope and the conventional transmission microscope according to the resolving power which the two instruments offer. The conventional microscope is capable of a point resolution of a few angstroms and line resolutions of periodic objects of about 1Å. On the other hand, the scanning microscope, in its normal form, is not ordinarily capable of a point resolution better than 100Å. Upon examining reasons for the 100Å limitation, it becomes clear that this is based more on tradition than reason, and in particular, it is a condition imposed upon the microscope by adherence to thermal sources of electrons.

Life Beyond 1MeV

1980 ◽  
Vol 38 ◽  
pp. 30-33
Author(s):  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
Past Experience ◽  
The Other ◽  
Good Case ◽  
Other Hand ◽  
The U.S

Life beyond 1MeV – like life after 40 – is not too different unless one takes advantage of past experience and is receptive to new opportunities. At first glance, the returns on performing electron microscopy at voltages greater than 1MeV diminish rather rapidly as the curves which describe the well-known advantages of HVEM often tend towards saturation. However, in a country with a significant HVEM capability, a good case can be made for investing in instruments with a range of maximum accelerating voltages. In this regard, the 1.5MeV KRATOS HVEM being installed in Berkeley will complement the other 650KeV, 1MeV, and 1.2MeV instruments currently operating in the U.S. One other consideration suggests that 1.5MeV is an optimum voltage machine – Its additional advantages may be purchased for not much more than a 1MeV instrument. On the other hand, the 3MeV HVEM's which seem to be operated at 2MeV maximum, are much more expensive.

Can the Academic Self-Concept be Positive and Realistic?

2005 ◽  
Vol 19 (3) ◽  
pp. 129-132 ◽  
Author(s):  
Reimer Kornmann
Keyword(s):  
Academic Performance ◽  
Opposite Effect ◽  
Self Esteem ◽  
Point Of View ◽  
The Other ◽  
Self Concept ◽  
High Ability ◽  
Self Image ◽  
Other Hand

Summary: My comment is basically restricted to the situation in which less-able students find themselves and refers only to literature in German. From this point of view I am basically able to confirm Marsh's results. It must, however, be said that with less-able pupils the opposite effect can be found: Levels of self-esteem in these pupils are raised, at least temporarily, by separate instruction, academic performance however drops; combined instruction, on the other hand, leads to improved academic performance, while levels of self-esteem drop. Apparently, the positive self-image of less-able pupils who receive separate instruction does not bring about the potential enhancement of academic performance one might expect from high-ability pupils receiving separate instruction. To resolve the dilemma, it is proposed that individual progress in learning be accentuated, and that comparisons with others be dispensed with. This fosters a self-image that can in equal measure be realistic and optimistic.

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