Brdnsted base

Reagent Strong bulky Brdnsted base (e.g., Me3CO ) Strong nucleophile... 

Table 3.4 Bjerrum s a parameter as calculated from c and x and corresponding properties of the proton. The ligands most often given away by both green plant roots and fungal mycelia produce a 0, making uptake of metal ions less sensitive towards pH changes even though certain of these ligands are fairly readily protonated, i.e. are considerable Brdnsted bases. This does not hold for those amino acids which are employed by grasses, mosses mainly, pointing to decreased selectivity...

The equilibrium of nucleophilic displacements favors the side with the weaker Brdnsted base the stronger Brdnsted base displaces the weaker Brdnsted base. The rate of the displacement reaction on the C of a given substrate depends on the nucleophilicity of the attacking base. Basicity and nucleophilicity differ as shown ... 

Brdnsted base (converting the catalyst to a solid Lewis acid) and then HF (due to decomposition of the boron trifluoride) can be monitored and used to determine catalyst stability as well as fine tune properties. 

Brpnsted acids are proton donors Brdnsted bases are proton acceptors. Strong acids transfer protons to alcohols to fonn alkyloxonium ions. An alkyloxonium ion is the conjugate acid of an alcohol. 

Ye, W., Jiang, Z., Zhao, Y. et a/. (2007) Chiral bicyclic guanidine as a versatile Brdnsted base catalyst for the enantioselective Michael reactions of dithiomalonates and P-keto thioesters. Advanced Synthesis and Catalysis, 349, 2454-2458. 

Write all the species (except water) that are present in a phosphoric acid solution. Indicate which species can act as a Br0nsted acid, which as a Brdnsted base, and which as both a Brdnsted acid and a Brdnsted base. 

Br0nsted acids donate protons, and Brdnsted bases accept protons. These are the definitions that normally underlie the use of the terms acid and base. 

Both the amide ion (NH2) and the nitride ion (N ) are stronger bases than the hydroxide ion and hence do not exist in aqueous solutions, (a) Write equations showing the reactions of these ions with water, and identify the Br0nsted acid and Brdnsted base in each case, (b) Which of the two is the stronger base ... 

In each case, the atom to which the proton becomes attached possesses at least one unshared pair of electrons. This characteristic property of OH , NH3, and other Brdnsted bases suggests a more general definition of acids and bases. 

Water is amphoteric, meaning it can act both as a Brdnsted acid and a Brdnsted base. 

All ionic hydrides are solids that have the high melting points characteristic of ionic compounds. The anion in these compounds is the hydride ion (H ), which is a very strong Brdnsted base. It readily accepts a proton from a proton donor such as water ... 

Brdnsted base, A substance that accepts a proton (H" ). (4.3,16.1) buffer. A solution that contains significant concentrations of both members of a conjugate pair (weak acid/conjugate base or weak base/conjugate acid). (17.2)... 

These reactions go nearly to completion in each case the reaction proceeds so that the stronger Bronsted base displaces the weaker Brdnsted base. For this reason, in most bimolecular reactions on carbon that go to completion, the leaving groups are the extremely weak bases, such as I , Br , and Cl . These anions are referred to as good leaving groups. ... 

On the other hand, a range of tV-allg lations of carbazoles can be achieved with secondary and hindered primary allgrl iodides or bromides under mild conditions with a simple precatalyst (Cul) in the presence of a Brdnsted base. The data are consistent with the formation of Li[Cu(carbazolide)2] under the coupling conditions and a possible role for this complex in the catalytic cycle. ... 

Surprisingly, preliminary results indicate that two of the new polymers, diaminofluorene and benzidine poly-para-phenylenediamine, could be Brdnsted base doped as determined spectroscopically. This result would complete the cycle of pH-dependent changes of physical properties of polyaniline. 

According to the Lowry-Brdnsted theory, a Brdnsted acid is a proton donor, while a Brdnsted base is a proton acceptor. In Lewis concept, acid acts as electron-pair acceptor, while base is electron donor (such as molecules possessing electton lone pairs). Hence, a Lewis base is in practice equivalent to a Brpnsted base. However, the concepts of acidity are markedly different [27]. 

In the case of solid catalysts, any atomic (ionic) group at the surface that can donate a proton is a Brdnsted acid while any place where one empty electron orbital exists is Lewis acid. For example, in the case of zeolites, Brdnsted acid site is a part of microporous aluminosilicate framework—a bridging [= Si (OH) A1 =] configuration which is able to donate a proton to an acceptor while Lewis acid site is either tri-coordinated A1 atom or charge-balancing cation Me " " which are able to accept the electron pair. Accordingly to the same theories, any place at the solid surface which can accept proton is a Brdnsted base while any place which can donate electron(s) is a Lewis basic site. For example, in the case of MeOjt (metallic oxides), the oxygen ions (0 ) behave as Brpnsted bases (because they are proton acceptors) while cations at the surface possess Lewis acidity (they are electron acceptors) [27, 28],... 

We have previously reported that photoluminescence from p-PS is reveribly quenched by the presence of non-hydroxide containing Brdnsted bases in either the gas or liquid phase.(7, 75) The quenching process involves an acid-base reaction between the quencher and the ground state p-PS surface. Neither of the postulated models immediately accomodates this observation. However, the confinement model appears to be easily modified to take into account the observed chemistry. 

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