Inductive effect of a substituent

Although cTi estimates by different methods or from different data sets may disagree, it is generally held that the inductive effect of a substituent is essentially independent of the nature of the reaction. It is otherwise with the resonance effect, and Ehrenson et al. have defined four different ctr values for a substituent, depending upon the electronic nature of the reaction site. An alternative approach is to add a third term, sometimes interpreted as a polarizability factor, and to estimate the inductive and resonance contribution statistically with the added parameter the resonance effect appears to be substantially independent of reaction site. " " ... 

The Avr = Avjncl — Av parameters are given in the Table 8. The Avm(j values characterize the inductive effect of a substituent only approximately31,115,116. Hence, also the Avr values may be used only for rough estimates of the inductive effect. The Avr values are positive in the series Me3MNMe2 for M = Si, Ge, Sn. Lower experimental values of Av in comparison with the expected ones based only on the inductive effect of the Me3M substituents (Avjnd) can be taken as evidence of the reduced n-donor properties of... 

Nevertheless, the inductive effect of a substituent is independent of the solvent used. Therefore, the slope of the linear correlations for water, acetone, and acetonitrile is the same (Figs. 49 and 50). The E values increase in the organic solvents (acetone and AN). This fact may be attributed to a greater stabilization of the oxidation +2 state of the clathrochelates in these solvents. 

The F-S term represents the inductive effect of a substituent at position 5. Since the coefficient is positive and large, it shows that an electron withdrawing group substantially increases activity. However, since only 2 compounds in the 61 synthesized had a 5-substituent, there might be quite an error in this result. 

Besides the dependence on the polar parameter ct (which characterizes the inductive effect of a substituent) the reaction rate depends also on the resonance... 

One final point is that we make no attempt to distinguish between the possible mechanisms for the transmission of the (r-effect of substituents. These are now commonly believed to encompass both field and through-bond effects (95,104). In our study, analyses associated with the field/inductive effects of a substituent are treated together under the heading of a effects. 

Inductive Effects The inductive effect of a substituent G arises from the electrostatic interaction of the polarized bond to G with the developing positive charge in the ring as it is attacked by an electrophile. If, for example, G is a more electronegative atom (or group) than carbon, then the ring will be at the positive end of the dipole ... 

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