Linear free energy enthalpy entropy relation for the ionization of benzoic acids

1972 ◽  
Vol 94 (3) ◽  
pp. 1033-1034 ◽  
Author(s):  
P. D. Bolton ◽  
K. A. Fleming ◽  
F. M. Hall
Keyword(s):  
Free Energy ◽  
Benzoic Acids ◽  
Linear Free Energy ◽  
Entropy Relation

The transmission of polar effects. Part VI. The ionization of ortho-substituted benzoic acids

1968 ◽  
Vol 46 (18) ◽  
pp. 2941-2944 ◽  
Author(s):  
Keith Bowden ◽  
G. E. Manser
Keyword(s):  
Free Energy ◽  
Benzoic Acid ◽  
Field Effect ◽  
Energy Relation ◽  
Benzoic Acids ◽  
Linear Free Energy ◽  
Free Energy Relation ◽  
Substituted Benzoic Acids ◽  
Reaction Constants

The pKa values of a series of ortho-substituted benzoic acids in 50% ethanol–water have been determined. The effect of ortho-substitution on the ionization of benzoic acid in this and other solvents has been correlated by a linear free energy relation. The reaction constants found are compared with those for the meta/para-substituted benzoic acids. While those for the former system are insensitive to changes in the medium, the latter vary considerably. It is suggested that this is due to transmission by the field effect passing almost entirely through the molecular cavity for ortho-substituents.

Hydrogen Atom Transfer Reaction Free Energy as a Predictor of Abiotic Nitroaromatic Reduction Rate Constants: A Comprehensive Analysis

2019 ◽  
Author(s):  
Dominic Di Toro ◽  
Kevin P. Hickey ◽  
Herbert E. Allen ◽  
Richard F. Carbonaro ◽  
Pei C. Chiu
Keyword(s):  
Free Energy ◽  
Hydrogen Atom ◽  
Hydrogen Atom Transfer ◽  
Energy Model ◽  
Second Order ◽  
Transfer Model ◽  
Atom Transfer ◽  
Order Rate ◽  
Linear Free Energy ◽  
Free Energy Model

<div>A linear free energy model is presented that predicts the second order rate constant for the abiotic reduction of nitroaromatic compounds (NACs). For this situation previously presented models use the one electron reduction potential of the NAC reaction. If such value is not available, it has been has been proposed that it could be computed directly or estimated from the electron affinity (EA). The model proposed herein uses the Gibbs free energy of the hydrogen atom transfer (HAT) as the parameter in the linear free energy model. Both models employ quantum chemical computations for the required thermodynamic parameters. The available and proposed models are compared using second order rate constants obtained from five investigations reported in the literature in which a variety of NACs were exposed to a variety of reductants. A comprehensive analysis utilizing all the NACs and reductants demonstrate that the computed hydrogen atom transfer model and the experimental one electron reduction potential model have similar root mean square errors and residual error probability distributions. In contrast, the model using the computed electron affinity has a more variable residual error distribution with a significant number of outliers. The results suggest that a linear free energy model utilizing computed hydrogen transfer reaction free energy produces a more reliable prediction of the NAC abiotic reduction second order rate constant than previously available methods. The advantages of the proposed hydrogen atom transfer model and its mechanistic implications are discussed as well.</div>

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