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.
References in periodicals archive ?
[14] had reported that the particle size of PdO2 over a plasma-treated sample was smaller than that in an untreated sample; hence the plasma-treated sample was of both the high dispersion of Bronsted and Lewis acid sites.
Niobium pentachloride is highly electrophilic, making possible act as a Lewis acid, have a low-cost commercial, and has been used by our group and other researchers as an effective catalyst in synthetic methodologies in a variety of reactions, obtaining excellent results [23, 29-30].
An excellent catalytic activity of 5.0 wt% Ni-HMETS-10 for the conversion of cellulose to LA was attributed to the synergistic effect of Lewis acid sites and unique hierarchical porous structures centered at 16 nm in ETS-10 in a [H.sub.2] atmosphere (Table 6, entry 6) [353].
In our preliminary studies, we have investigated the onepot multicomponent reactions of different aromatic aldehydes with malononitrile and primary amines, using various Lewis acids such as Zn[Cl.sub.2], Al[Cl.sub.3], and Fe[Cl.sub.3] in ethanol as a solvent with different molecular ratios.
Table 2 presents data on the concentration of the Lewis acid sites because Bronsted centers capable of protonating pyridine (region between 1530 and 1550 [cm.sup.-1] ([nu]CCN 19b)) have not been found.
In this glycosylation reaction, it is assumed that Sn[Cl.sub.2] behaves as a Lewis acid where the vacant orbital accepts one of three lone pairs on the fluorine atom of the glycosyl fluoride.
Polymerizations were performed in a double wall 2 L steel reactor, which was purged with nitrogen before the addition of organic solvent, metal complex, activators), Lewis acids or other components.
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.
Finally applications of iron-containing complexes to specific chemical transformations are discussed, including reductions, asymmetric synthesis, Lewis acid catalysis, C-C bond formation with C-H bond activation, and cross-coupling.
3:45 LEWIS ACID CATALYZED 2.3-REARRANGMENTS OF O-ALLYLHY-DROXYLAMINES **.
Determination of acidity aims to determine the amount of acid sites available on the Si[O.sub.2]-[Al.sub.2][O.sub.3]/bentonite nanocomposite and Na-bentonite in each sample weight (mmol/g) both Bronsted acid sites and Lewis acid sites without seeing how strong acidic sites.
Silica can potentially create Lewis acid sites and the mixed silica alumina coating can possess both acid and basic sites.(31-41)The acid sites have the ability to adsorb amine containing organic molecules and hence interact with DICY.

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