Lewis acid


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Related to Lewis acid: Bronsted acid

Lewis acid

[′lü·əs ‚as·əd]
(chemistry)
A substance that can accept an electron pair from a base; thus, AlCl3, BF3, and SO3 are acids.
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2], a fairly weak Lewis acid at room temperature, giving rise to 1,2-cis-glycosides that are difficult to prepare compared to the 1,2-transglycosides.
Therefore, both methylalumoxane A and tetrakis-pentafluorophenyl-borane F in combination with an alkylating Lewis acid proved to be excellent activating agents.
For most carbocationic polymerizations of a vinyl ether produced using a Lewis Acid coinitiator, such as ethylaluminum sesquichloride, an appropriate concentration of Lewis base is needed to obtain a living polymerization.
3] Lewis acid as well as Br0nsted acid increases the number of sites that has a chance to absorb large amounts of pyridine.
The procedure is based on molecules called Lewis bases, which carry a lone pair of electrons and can bond with so-called Lewis acids to make a molecule called an adduct.
These Lewis acids can bind the cis-1,2- or -1,3diols of glucose covalently to form 5- or 6-part rings.
Steinert, organometallic compounds use a Lewis acid mechanism and he provided an example of the curing diagram.
In his work to replace the Friedel-Crafts reaction - which involves an acid chloride or anhydride and a benzene-type compound in the presence of a Lewis acid - Kraus has focused on the synthesis of benzodiazepines, which include the drug Valium.
18] reported that Bronsted acid sites are generated by exchange of inter-lamellar cations with protons and Lewis acid sites correspond to Mg2+ and Al3+ present at the edges of octahedral sheets.
Objective: In the frame of this research program, carried out at the Institute of Molecular Sciences (ISM) within the University of Bordeaux (UB), we propose the development of new powerful Lewis acid catalysts for asymmetric synthesis.
It is known that aziridines are not reactive towards nucleophilic compounds unless the nitrogen has been quatemized, protonated or has formed a Lewis acid adduct.

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