Characterization of Substituents by Patterns and Recognition of ALTERNATIVE PRINCIPLES

Abstract

Up to 1979 about 5.000–10.000 applications of FE- (free energy) or LFE- (linear free energy) relations in organic chemistry are described in the literature. This distinctly demonstrates the importance of detection and description of quantitative changes e.g. in chemical reactivity of parent systems (a determining and invariant constituent of a whole system). Hammett-, Taft- and other parameters [51,52] are applied to account for the effects of variable substituents in carbon-σ-and -π-systems. More seldom, corresponding parameters are put to the successful description of quantitative changes in kinetic or thermodynamic values of metal-induced or -catalyzed processes (see e.g. [53–55]). Within the framework of this chapter, we will, at the beginning, restrict ourselves to the application of those parameters referring to the properties of phosphanes and phosphites (P-ligands). Overwhelmingly, we will demonstrate, by pattern recognition, that we are able to characterize in more detail the ordering power of organic substituents.

The sort of thinking that deals with quantity resembles in many ways the thinking that surrounds the concept of energy; whereas the concept of number is much more closely related to the concepts of pattern and negentropy

G. Bateson [9]