Acidity soft and hard

Covalent Interactions in Zeolites The Influence of Zeolite Composition and Structure on Acid Softness and Hardness... 

Corma A Covalent interactions in zeoiites the influence of zeolite composition and structure on acid softness and hardness. Stud Surf Sci Catal 1995, 94 736-747. 

Corma A, Llopis F, Viruela P, Zicovich Wilson CM Acid softness and hardness in large pore zeolites as a determinant parameter to control selectivity in orbital controlled reactions. 

Displacement reactions and the concept of soft and hard acids and bases. Struct. Bonding (Berlin), 1966,1,221-233(19). 

Soft and hard acids and bases principle, 2, 1040 Soft-tissue calcification, 6,597 Sogrenite structure, 6, 849 Soils... 

Hudson RF (1966) Displacement Reactions and the Concept of Soft and Hard Acids and Bases. 1 221-223... 

The first task is to decide whether the members of a given group are Lewis acids or bases. Then evaluate the relative softness and hardness based on polarizability, taking into account correlations with electronegativity, size, and charge. Refer to the periodic table in assessing the trends. 

Table 4 contains the E and C parameters for the donors presently in the correlation. Calculation of the C/E ratio from data in Table 4 indicates, as it does for the acids in Table 3, that a large variety of different types of species are present. According to the soft and hard classification, the donors are categorized as follows (2) ... 

Next, we shall describe why the magnitudes of the E and C numbers are not just quantitative manifestations of the HSAB concept, but give insight into intermolecular interactions which are absent in the qualitative soft-soft and hard-hard labeling of interactions. As can be seen from the data in Tables 3 and 4, each acid and base has both a C and an E number which could be thought to correspond to possessing properties of softness and hardness. If this were the case, ammonia, which Pearson labels hard, has a larger Cb value than benzene, which is labeled soft. 

The first symposium on soft and hard (Lewis) acids and bases was organized by Prof. R. F. Hudson (now at the University of Kent, Canterbury) at our institute in May 1965, and the proceedings partly published in Structure and Bonding 1, pp. 207—248. A second symposium was organized by Professor Malcolm J. Frazer, Northern Polytechnic, Holloway, London, 29.—31. March 1967. The proceedings of this discussion were not published, but the present paper is based on the invited lecture, partly modified after further helpful comments by Professors /. Bjerrum, K. Fajans and G. Klopman. 

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