نتایج جستجو برای: hammett

تعداد نتایج: 424  

Journal: :Tetrahedron 2022

Preliminary validation of cyclopropene activation by an I(I)/I(III) catalysis manifold is disclosed to enable the direct tetrafluorination 3,3-diarylcyclopropenes. This transformation occurs through in situ generation ArI(III)F2, with inexpensive iodobenzene, amine·HF complexes and Selectfluor® serving as catalyst, fluoride source oxidant, respectively. Leveraging this approach, it has been pos...

Journal: :Chemcatchem 2022

Low-valent titanocene catalysts are a versatile tool for organic synthesis. They promote inter- and intramolecular reactions ranging from homolytic bond cleavages to reductive umpolung additions cyclizations in single electron steps. These heavily depend on the redox potential of an situ formed titanium(III) center, which can be adjusted by choice appropriate ligands. We herein review various c...

Journal: :Organometallics 2006
Chae S Yi Tonya N Zeczycki Ilia A Guzei

The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy(3))(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} (1) was synthesized in two steps from the monomeric complex (PCy(3))(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern towards primary and secondary benzy...

2014
Wei Xue You-Chun Zhou Bao-An Song Xia Shi Jun Wang Shi-Tao Yin De-Yu Hu Song Yang

An environmentally benign process was developed for the transesterification of Jatropha curcas L. seed oil with methanol using artificial zeolites loaded with potassium acetate as a heterogeneous catalyst. After calcination for 5 h at 823 K, the catalyst loaded with 47 wt.% CH3COOK exhibited the highest efficiency and best catalytic activity. The easily prepared catalysts were characterized by ...

Journal: :Vision Research 1996
John Ross Harriet D. Speed

Using a contrast matching procedure, we measured the perceived contrast of vertical test gratings after adapting to other gratings of either vertical or horizontal orientation. The results show that both parallel and orthogonal adapting gratings reduce perceived contrast and do so proportionally more at low test contrasts than at high. The results are consistent with a single mechanism model pr...

2004
Benoı̂t Louis Lioubov Kiwi-Minsker

ZSM-5 zeolites were prepared at neutral pH by fluoride-mediated synthesis. The degree of crystallinity, the specific surface area and the crystal size are higher than those of the zeolites prepared under alkaline conditions. Moreover, by varying the F/Si ratio from 0.3 to 1.6, the H–[F]–ZSM-5 zeolites with crystal size ranging from 10 to 75 lm and the specific surface areas from 60 up to 350 m/...

2014
K. P. SRIVASTAVA

The rates of zinc chloride (Lewis acid) catalysed oxidation of thioanisole and several para-substituted thioanisoles by permanganate have been studied in anhydrous acetone solutions. The kinetic rate law obtained indicates that a complex between permanganate and the Lewis acid (ZnCl2) is formed before oxidation of the sulfur-containing compounds occurs. The function of the zinc chloride is to e...

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