Electrical effects parameters

C. Estimation of Electrical Effect Parameters for Dienyl and Polyenyl... 

From quantum chemical calculations2 3. This method is most suitable for electrical effect parameters. 

It is often necessary to estimate values of electrical effect parameters for groups for which no measured values are available27. The equations available for the estimation of ai values for traws-vinylene (CH=CHZ) and vinylidene (CZ=CH2) groups are ... 

These Xpjr groups represent an especially difficult problem because their delocalized electrical effect depends on the steric effect when they are bonded to planar jr-bonded skeletal groups, Gp7r. An approach to the problem has been developed45,46. The electrical effect parameters are a function of the dihedral angle formed by Xp3r and Gpn. The relationship generally used has the form ... 

Ui is the intrinsic delocalized (resonance) electrical effect parameter it represents the delocalized electrical effect in a system with no electronic demand. 

The electronic demand, r, is a property of a system or of a composite electrical effect parameter that is itself a function of both and a. It is defined as RjD, where R and D are the coefficients of and respectively. 

A monoparametric equation results when a composite electrical effect parameter is obtained by combining all three pure electrical effect parameters with fixed values of both Pd and t]. The Hammett substituent constants are of this type. The Hammett equation is given by equation 5 ... 

The magnitude of p is in accord with a reaction at a ring C atom. Winkler and Winkler have also reported equilibrium and rate constants (sets CR7 and CR8, Table 9). We described above a modified Yukawa-Tsuno (MYT) equation (equation 6) with a taking the value for 3-substituted benzene derivatives and <750 for 4-substimted benzene derivatives, while for substituents in the meta position is 0. For this application the appropriate value of was unknown and all three pure electrical effect parameters were used for the para substituents thus the MYT equation used was equation 37 ... 

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