Electrical effect substituent constants

Values of electrical effect substituent constants for a few dienyl and polyenal groups have been reported25. They are set forth in Table 1 together with values of diynyl and phenyl groups for comparison. Also reported in Table 1 are values for some other types of substituents22,25 for purposes of comparison. 

The use of the methyl group as the reference substituent meant that they were not compatible with electrical effect substituent constants for which the reference substituent is hydrogen. 

These interactions (dd, di, ii) are a function of dipole moment and polarizability. It has been shown that the dipole moment cannot be replaced entirely by the use of electrical effect substituent constants as parameters52. This is because the dipole moment has no sign. Either an overall electron donor group or an overall electron acceptor group may have the same value of /x. It has also been shown that the bond moment rather than the molecular dipole moment is the parameter of choice. The dipole moments of MeX and PhX were taken as measures of the bond moments of substituents bonded to sp3- and sp2-hybridized carbon atoms, respectively, of a skeletal group. Application to substituents bonded to sp-hybridized carbon atoms should require a set of dipole moments for substituted ethynes. 

Methods have been presented, with examples, for obtaining quantitative structure-property relationships for alternating conjugated and cross-conjugated dienes and polyenes, and for adjacent dienes and polyenes. The examples include chemical reactivities, chemical properties and physical properties. A method of estimating electrical effect substituent constants for dienyl and polyenyl substituents has been described. The nature of these substituents has been discussed, but unfortunately the discussion is very largely based on estimated values. A full understanding of structural effects on dienyl and polyenyl systems awaits much further experimental study. It would be particularly useful to have more chemical reactivity studies on their substituent effects, and it would be especially helpful if chemical reactivity studies on the transmission of electrical effects in adjacent multiply doubly bonded systems were available. Only further experimental work will show how valid our estimates and predictions are. 

Electrical effect substituent constants for group 14 elements other than carbon have... 

Values of electrical effect substituent constants for typical groups are presented in Tables 1-3. 

TABLE 1. Electrical effect substituent constants for common substituents"... 

Values of electrical effect substituent constants for oxime and hydroxylamino groups have been reported ° their values are set forth in Tables la-c. No value for the acid group, CO(NHOH), was available. We have estimated values for it they are given in Tables la-c. Also in Tables la-c are values for some other types of substituents either for purposes of comparison or because they were used in correlations in this work. 

We now consider the problem of the calculation of delocalized electrical effect substituent constants, crD, which correspond to a particular value of the dihedral angle 0, of the group. From the geometry previously determined for this type of system (Fig. 13) we may define the effective Van der Waals radius of the Xptt group MZ Z2 as... 

The second type of tetracoordinate Group 15 substituent is the ionic group [MZ Z Z ] . Unfortunately we are not yet able to estimate the electrical-effect substituent constants of ionic groups and have been therefore unable to discuss them. 

We have estimated values of electrical-effect substituent constants for only two examples of MZ groups those where Z is fluorine or phenyl. We believe that the estimated direct evidence that our model is suitable for their estimation. We are therefore unable to discuss the electrical effects of these groups at this time. 

Charton, M. (1981). Electrical Effect Substituent Constants for Correlation Analysis. Prog.Phys. Org.Chem., 13,119-251. 

Electrical Effect Substituent Constants for Correlation Analysis... 

C. Definition of Localized Electrical Effect Substituent Constants.131... 

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