On the nature of modified composite electrical effect parameters

Autor: Barbara I. Charton, Marvin Charton
Rok vydání: 2003
Předmět:
Zdroj: Journal of Physical Organic Chemistry. 16:715-720
ISSN: 1099-1395
0894-3230
DOI: 10.1002/poc.636
Popis: It is shown that a correlation of some property, reactivity or biological activity with pure parameters can also be carried out with composite parameters to produce a model with comparable statistics. Modified composite electrical effect parameters can be obtained from known composite electrical effect parameters by means of an algorithm such as σX♦ = (σX + c)m in which σX♦ is the modified composite electrical effect parameter (MCEEP), σX the original composite electrical effect parameter, c a constant and m an exponent. MCEEPs were calculated from this equation with c equal to 2 and m ranging from −4 to 4 when σX is σm or σp, and from −2 to 2 when it is σp+. They were used to model 10 sets of chemical reactivities that had previously been correlated with the pure parameters σ1, σd and σe, which represent the localized (field), intrinsic delocalized (resonance) and electronic demand sensitivity electrical effects, respectively. In most cases both the pure and the modified composite parameters give comparable fits to the data as measured by the values of 100R2, in accord with the prediction. The composition of the MCEEPs was a linear function of m. The advantage in using pure parameters is that they are readily interpretable. Correlations with composite parameters can be interpreted only if their composition has been determined. These results provide an understanding of the way in which topological parameters work. Copyright © 2003 John Wiley & Sons, Ltd.
Databáze: OpenAIRE
Externí odkaz: