Theoretical studies Bronsted acidity

Whereas the proton (H ) can be considered the ultimate Bronsted acid (having no electron), the helium dication (He ) is an even stronger, doubly electron-deficient eleetron aceeptor. In a theoretical, calculational study we found that the helionitronium trication (NOaHe" ) has a minimum structure isoelectronic and isostructural... 

Savoskin M.V., Yaroshenko A.P., Whyman G.E., Mestechkin M.M., Mysyk R.D., Mochalin V.N. Theoretical study of stability of graphite intercalation componds with Bronsted acids. Carbon 2003 41 2757-60. 

In summary, the direct quantum mechanical simulation of zeolite vibrational spectra is evidently a formidable task and is often severely hampered by limited computational resources. Pure ab initio methods are well-suited if local effects or groups with characteristic vibrational frequencies like Bronsted acidic OH groups are under study. In theoretical studies of vibrational spectra of zeolite frameworks and cations on extra-framework sites, QM calculations are of crucial importance in developing force field parameters which can be used in a subsequent step in MM, MD or NMA calculations. Due to the lack of sufficient exper-... 

A theoretical study using the density functional theory (DFT) method has been performed to rationalize the mechanism of the reactions between 1,3-dialkynes and hydroxylamine or hydrazine for the formation of 3,5-disubstituted isoxazoles or pyrazoles, respectively The computational results support a bimolecular proton transfer as the rate-determining step providing valuable clues for the use of Bronsted acid/base catalysts to promote the cyclization reaction (14OBC7503). 

Briones-Jurado, G. and Agacino-Vald s, E. 2009. Bronsted sites on acid-treated montmorillonite A theoretical study with probe molecules. Journal cf Physical Chemistry A 113 8994r-9001. 

Previously, comprehensive theoretical studies have been made to explore the correlations between the Bronsted acidic strength and 8 P of adsorbed R3PO by DFT calculations [18,25]. Accordingly, the adsorption... 

N. Feng, A. Zheng, S.J. Huang, H. Zhang, N. Yu, C.Y. Yang, S.B. Liu, F. Deng, Combined solid-state NMR and theoretical calculation studies of Bronsted acid properties in anhydrous 12-molybdophosphoric acid, J. Phys. Chem. C 114 (2010) 15464-15472. 

Tsutsumi et al. have studied heats of ammonia adsorption on mordenites with different Si / Al ratio [88]. The number of acid sites determined from the heat curves plotted against the theoretical number of protons (aluminum atoms) per unit cell of mordenites, shows a slope that deviates little from unity (Fig. 9.4) the deviation being smaller for higher Si / Al ratios. The authors suggested that the framework aluminium atoms participate in the formation of acid sites and that some of the generated Bronsted acid sites are converted to Lewis acid sites. Displacement of aluminium atoms from the zeolite framework may also be responsible for the observed deviation. 

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