Relationships between Structure and Reactivity

The most notable studies are those of Ingold, on the orienting and activating properties of substituents in the benzene nucleus, and of Dewar on the reactivities of an extensive series of polynuclear aromatic and related compounds ( 5.3.2). The former work was seminal in the foundation of the qualitative electronic theory of the relationship between structure and reactivity, and the latter is the most celebrated example of the more quantitative approaches to the same relationship ( 7.2.3). Both of the series of investigations employed the competitive method, and were not concerned with the kinetics of reaction. 

These rate constants are for the cinnamoylation of hydroxy compounds by cinnamic anhydride catalyzed by A-methylimidazole. The reaction is first-order in each reactant. The kinetics were followed spectrophotometrically in acetonitrile solution. Analyze the data that is, attempt to account for the relationship between structure and reactivity. 

The reactivity of substituted aromatic compounds, more than that ol any other class of substances, is intimately tied to their exact structure. As a result, aromatic compounds provide an extraordinarily sensitive probe for studying the relationship between structure and reactivity We ll examine that relationship in this and the next chapter, and we ll find that the lessons learned are applicable to all other organic compounds, including such particularly important substances as the nucleic acids that control our genetic makeup. 

A fundament of the quantum chemical standpoint is that structure and reactivity are correlated. When using quantum chemical reactivity parameters for quantifying relationships between structure and reactivity one has the advantage of being able to describe the nature of the structural influences in a direct manner, without empirical assumptions. This is especially valid for the so-called Salem-Klopman equation. It allows the differentiation between the charge and the orbital controlled portions of the interaction between reactants. This was shown by the investigation of the interaction between the Lewis acid with complex counterions 18> (see part 4.4). 

The opinion that stabilization of 1 by resonance was decisive, predominated for a long time and mastered the discussion of the relationship between structure and reactivity in free radical chemistry till quite recently5 Accordingly selectivity in free radical reactions was assumed to be mainly due to differences in the thermodynamic stability of the radicals taking part in a reaction or a potential competing reaction. 

Woodall, A.A., Lee, S.W.-M., Weesie, R.J., Jackson, M.J., and Britton, G. 1997a. Oxidation of carotenoids by free radicals Relationship between structure and reactivity. Biochim. Biophys. Acta 1336 33 12. 

Catalytic Materials Relationship Between Structure and Reactivity... 

In Catalytic Materials Relationship Between Structure and Reactivity Whyte, T., el al. ACS Symposium Series American Chemical Society Washington, DC, 1984. 

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