Lower Bounds to Hammett σ Constants for meta and para Normal Substituents

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Title:Lower Bounds to Hammett σ Constants for meta and para Normal Substituents
Creators:
Reis, João Carlos R.
Segurado, Manuel A. P.
Gomes de Oliveira, Jaime D.
Journal or Publication Title:
Collection of Czechoslovak Chemical Communications, 64, 10, pp. 1607-1616
Uncontrolled Keywords:Chemometrics, <i>meta/para</i> Ratio, Hyperbolic model, Hammett equation, Through-space interactions, Substituent effects, Substituent constants

Abstract

Twenty-four pairs of <i>meta</i> and <i>para</i> Hammett σ constants recommended by IUPAC for normal substituents, <i>i.e.</i> dipolar groups without a lone pair of electrons (and with a full octet) in the atom next to the aromatic ring, were analysed with respect to their <i>meta</i>-<i>para</i> interrelationship. In terms of a previous hyperbolic model, the <i>para/meta</i> ratio of the universal electric effect is found to be 0.964 with a standard error of 0.028 estimated by Monte Carlo simulation. This value for benzoic acid derivatives supports the view that the universal electric effect, which is proposed to be termed the Electra effect, is transmitted through space. For normal substituents, it is demonstrated that the hyperbolic model predicts lower bounding values of σ<i><sub>m</sub></i> and σ<i><sub>p</sub></i> constants. It is proposed that organometallic substituents in which a metallic atom is bounded to the α carbon should not be considered as normal substituents. It is asserted that no normal substituent should exist for which either σ<i><sub>m</sub></i> is less than -0.1 or σ<i><sub>p</sub></i> is less than -0.3 in the Hammett σ scale. <p>

Title:Lower Bounds to Hammett σ Constants for meta and para Normal Substituents
Creators:
Reis, João Carlos R.
Segurado, Manuel A. P.
Gomes de Oliveira, Jaime D.
Uncontrolled Keywords:Chemometrics, <i>meta/para</i> Ratio, Hyperbolic model, Hammett equation, Through-space interactions, Substituent effects, Substituent constants
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:64
Number:10
Page Range:pp. 1607-1616
ISSN:0010-0765
E-ISSN:1212-6950
Publisher:Institute of Organic Chemistry and Biochemistry
Related URLs:
URLURL Type
http://dx.doi.org/10.1135/cccc19991607UNSPECIFIED
ID Code:1583
Item Type:Article
Deposited On:06 Feb 2009 17:10
Last Modified:06 Feb 2009 16:10

Citation

Reis, João Carlos R.; Segurado, Manuel A. P.; Gomes de Oliveira, Jaime D. (1999) Lower Bounds to Hammett σ Constants for meta and para Normal Substituents. Collection of Czechoslovak Chemical Communications, 64 (10). pp. 1607-1616. ISSN 0010-0765

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