Defined inductive effects

Hammett relations used to define inductive effects of substituents in a benzene ring on dissociation constants of acids (see p. 60) can provide a systematic approach to evaluate the inductive effects of substituents on the hydrolysis of esters. The indue-... 

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. " " ... 

Another study by Neta and coworkers169, on the redox chemistry of several metallo-porphyrins in aqueous solution where metals were Zn, Pd, Ag, Cd, Cu, Sn and Pb, shows them to have well defined oxidation and reduction steps, yet the metals seem to exert merely an inductive effect on the porphyrin tt level. 

The Hammett equation has been further extended to include substituents of aliphatic systems too. In this case the constants that quantify the inductive effects, which are represented as o, have different values compared to those concerned with aromatic systems and are defined as Taft constants. Some values of these latter are also reported in Table 1. 

Topsom, 1976) and to treat them separately. In this review we will be concerned solely with polar or electronic substituent effects. Although it is possible to define a number of different electronic effects (field effects, CT-inductive effects, jt-inductive effects, Jt-field effects, resonance effects), it is customary to use a dual substituent parameter scale, in which one parameter describes the polarity of a substituent and the other the charge transfer (resonance) (Topsom, 1976). In terms of molecular orbital theory, particularly in the form of perturbation theory, this corresponds to a separate evaluation of charge (inductive) and overlap (resonance) effects. This is reflected in the Klopman-Salem theory (Devaquet and Salem, 1969 Klop-man, 1968 Salem, 1968) and in our theory (Sustmann and Binsch, 1971, 1972 Sustmann and Vahrenholt, 1973). A related treatment of substituent effects has been proposed by Godfrey (Duerden and Godfrey, 1980). 

The asymmetric inducting effect of the chiral pyranic ring placed outside of the six centers of the chair transition state has to be noted. In the present case, magnesium dihalide seems to play a crucial role in terms of stereocontrol as an efficient tool to fix a defined... 

The term polar effect refers to the influence, other than steric, that nonconjugated substituents exert on reaction rates. It does not define whether the mechanism for its transmission is through bonds (inductive effect) or through space (field effect). 

The inductive effect, as many other effects in organic chemistry, is not an observable and cannot be defined precisely, in an objective manner. It is therefore not surprising that different criteria led to different conclusions. See Minot et al.16 for a more detailed discussion. 

Pure sulfuric acid is a stronger acid than sulfuric acid in water because the acid in aqueous sulfuric acid is actually H30+. Superacids are defined as compounds that are even stronger acids than 100% H2S04. One example of a superacid is fluoiosulfonic acid. The inductive effect of the electronegative fluorine makes this a stronger acid than sulfuric acid. 

In Section 2.4, the concept of relative acidities was presented without fully defining the concept of inductive effects. In Section 2.5, the concept of inductive effects was defined and linked to functional groups. In this section, the concept of relative acidities is presented in conjunction with discussions of associated functional groups and their respective inductive effects. Since a treatment of this subject was already introduced in Section 2.4 as applied to carboxylic acids and esters, this section focuses on... 

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