General Remarks About Reactivity

Edwards and Pearson [37] have proposed qualitative relationships between the reactivity of nucleophiles and their basicity and polarisability. Anions, such as cyanide, thiolate, sulfide and iodide were used to obtain quantitative reactivity data, 

The HSAB-principle may be criticized as being too opportunistic the qualitative hard and soft assignments for reacting centers are used to explain rather small regio preferences, which reflect energy differences of only a few tenths of a Kcal/mol. However, the HSAB-principle is soundly based [41]. Basicity and polarisability may be used (with care) to predict qualitatively relative reactivities of a series of nucleophilic species. 

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Some general remarks about structure-reactivity relationships in radical reactions can be made at this point. Other examples of structural effects on reactivity will... 

The alkali metals remarks about their general chemical properties and reactivity... 

As a conclusive remark about this topic we underline that the trend of the inter-metallic reactivity described for the 3rd group metals and the phase stability scheme shown may be considered an example of a systematic alloying behaviour generally presented by several metals of the first groups of the Periodic Table. The reader may indeed compare the patterns here reported in Fig. 5.14 with those previously presented for the 2nd group metals and with those shown in the next paragraphs for the metals of the 4th group. 

It is remarkable that the work by Heitler and London that outlined for the first time a physically correct description of the chemical bond did not replace the Lewis picture of electron-pair bonding that was based on intuition rather than on elementary physics. One reason is the dramatically different appeal of the two approaches for human imagination of the chemical bond. The Lewis picture is simple to use and it proved as extremely powerful ordering scheme for molecular structures and reactivities. Chemists are generally happy with such models. The quantum theoretical description of interatomic interactions introduced the wave function as the central term for chemical bonding, which is in contrast an elusive object for human imagination, as evidenced by the intensive discussions about the meaning and the interpretation of P mainly in the physics community. 

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