Br0nsted acidity

Figure C2.12.2. Fonnation of Br0nsted acid sites in zeolites. Aqueous exchange of cation M witli an ammonium salt yields tlie ammonium fonn of tlie zeolite. Upon tliennal decomposition ammonia is released and tire proton remains as charge-balancing species. Direct ion-exchange of M witli acidic solutions is feasible for high-silica zeolites.

Clearly the two reactions are analogous and demonstrate that the reaction between hydroxide ion and hydrogen bromide is simultaneously a Brpnsted acid-base reaction and a Lewis acid Lewis base reaction Br0nsted acid-base reactions constitute a sub category of Lewis acid Lewis base reactions... 

Dissociation Constants for Selected Br0nsted Acids (Table 4 2, p 135)... 

BR0NSTED-ACID-CATALYZED DIELS-ALDER REACTION... 

Br0nsted-Acid-Catalyzed Diels-Alder Reaction... 

In two recent papers [8,10], we have initiated studies aimed at understanding the catalytic behavior of WZ and PtWZ. Our observations, which motivated the present study, can be summarized as follows, a) Water of reduction results in the formation of Br0nsted acid sites, as monitored by pulsed addition of pyridine to a DRIFTS chamber at room temperature [8,10]. In this paper, we have complemented those results with similar pyridine adsorption experiments at... 

Harrison [57] distinguishes Br0nsted acid and base chemical ionisation, charge exchange (CE) and electron capture chemical ionisation (ECCI). 

The ability of the Si=P bond to serve as a dienophile for a [2+4]-cycloaddition (hetero-Diels-Alder reaction) has been verified by the reaction of 15a with cyclopentadiene (Eq. 10).14 The components react at 60°C in benzene to give a quantitative yield of 25, which was isolated as a colorless solid. Interestingly, a Br0nsted acid (C—H)/base (Si=P) reaction, as in the case of 15a and phenylacetylene, was not observed. In the mass spectrum of25, the molecular peak but also the free phosphasilene 15a+ have been detected. Similar behavior was observed for related ad-... 

Lewis acid site Br0nsted acid site ... 

Two-Dimensional correlation analysis to study Br0nsted acid sites in zeolites... 

K. Motokura, N. Nakagiri, T. Mizugaki, K. Ebitani, and K. Kaneda, Nucleophilic substitution reactions of alcohols with use of montmorillonite catalysts as solid Br0nsted acids, J. Org. Chem., 72 (2007) 6006-6015. 

Reductive Etherification. As indicated earlier, aldehydes as well as ketones often give very good yields of ethers when they are treated with Br0nsted acids or other electrophilic species in the presence of organosilicon hydrides (Eq. 172). In the absence of added alcohols, symmetrical ethers are obtained. 

Cj) Treatment of zero-valent nickel complexes with Br0nsted acids. 

It is generally assumed that the electron donor can have one or several of the following functions to increase the stability of the catalytically active species to increase the catalytic activity of the catalyst to allow a control over the selectivity of the catalytic reaction or to increase the solubility of the catalyst in organic media. The main effect of Lewis or Br0nsted acids is to increase the catalyst activity, but their influence on selectivity control is not considered to be of great significance (see, however, Sections IV,D,2 and IV,F). The increase in activity of the catalyst (see below) on the addition of Lewis or Brdnsted acids is frequently accompanied by a decrease in stability of the system. 

In this section charges on cations or anions are omitted for sake of generality. L and H.L are used to symbolize a ligand and the corresponding uncharged Br0nsted acid. The conventional symbols used for equilibrium constants are similar to those described in Ref. (8). 

Table 6.1 Typical properties of Lowry-Br0nsted acids...

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