Chemometric Analysis of Substituent Effects. X. Unification and Reparametrization of Substituent Constants in Hammett-Type Equations by Means of Alternative Interpretation of Substituent Effects (AISE)

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Title:Chemometric Analysis of Substituent Effects. X. Unification and Reparametrization of Substituent Constants in Hammett-Type Equations by Means of Alternative Interpretation of Substituent Effects (AISE)
Creators:
Pytela, Oldřich
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 61, 8, pp. 1191-1204
Uncontrolled Keywords:Alternative interpretation of substituent effects, Hammett equation, Substituent effects

Abstract

The paper deals with evaluation of validity of substituent scales σ<i><sub>m</sub></i>, σ<i><sub>p</sub></i>, σ<i><sub>p</sub></i><sup>0</sup>, σ<i><sub>p</sub></i><sup>+</sup>, and σ<i><sub>p</sub></i><sup>-</sup> in Hammett-type equations. Possible reasons of unreliability of these scales and conceivable ways of verification of individual substituent constants are discussed. On the basis of Alternative Interpretation of Substituent Effects (AISE) and four additional conditions, a regression nonlinear model has been suggested which includes the dependence of all above-mentioned substituent scales upon a single interpreting variable - the σ<i><sup>i</sup></i> substituent constant. This model has been applied to the 32 most frequent substituents from each scale, i.e. altogether 160 substituent constants taken from literature. The optimization of 17 unknown regression parameters gave the residual standard deviation <i>s</i> = 0.180 and, after excluding 12 remote values, <i>s</i> = 0.061. The analysis of residua proved their standard and statistical appropriateness of the model. The agreement between literature values and predicted values of substituent constants was the best with the σ<sub><i>m</i></sub> scale; on the other hand, the largest differences were encountered with the σ<i><sub>p</sub></i><sup>+</sup> scale. The found differences above a current reliability limit of substituent constants were due first to unreliability of some literature data and next to solvent effects and (in some cases) specific properties of substituents.

Title:Chemometric Analysis of Substituent Effects. X. Unification and Reparametrization of Substituent Constants in Hammett-Type Equations by Means of Alternative Interpretation of Substituent Effects (AISE)
Creators:
Pytela, Oldřich
Uncontrolled Keywords:Alternative interpretation of substituent effects, Hammett equation, Substituent effects
Divisions:Life and Chemical Sciences > Institute of Organic Chemistry and Biochemistry > Collection of Czechoslovak Chemical Communications
Journal or Publication Title:Collection of Czechoslovak Chemical Communications
Volume:61
Number:8
Page Range:pp. 1191-1204
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19961191UNSPECIFIED
ID Code:1024
Item Type:Article
Deposited On:06 Feb 2009 17:05
Last Modified:06 Feb 2009 16:06

Citation

Pytela, Oldřich (1996) Chemometric Analysis of Substituent Effects. X. Unification and Reparametrization of Substituent Constants in Hammett-Type Equations by Means of Alternative Interpretation of Substituent Effects (AISE). Collection of Czechoslovak Chemical Communications, 61 (8). pp. 1191-1204. ISSN 0010-0765

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