Application of the Hammett equation in the esterification of substituted benzoic acids, catalyzed by AlPO4 in the gas phase

The Hammett equation has for the first time been applied to the esterification in the gas phase of m-MeO, p-MeO, m-Me, p-Me, H, m-NO2, m-Cl, and m-Br benzoic acids, catalyzed by AlPO4 of the F type. It is shown that the Hammett equation could be applied to the adsorption equilibrium constant, KA, and to the apparent kinetic constant, [Formula: see text] The KA and [Formula: see text] values used in this paper have been taken from a study by the same authors. The m-NO2 benzoic acid is in disagreement with the general behavior of the other acids in the application of the Hammett equation to the adsorption process. The p-MeO benzoic acid is in disagreement with the behavior of the acids in the application of the equation to the surface reaction. In these cases, the ρ values were negative. It can be deduced that a positive charge is generated in the adsorption process and in the surface reaction. The AAc2 mechanism is discussed according to the values of ρ, and a more detailed mechanism is proposed. The separation of the enthalpic and entropic contributions to the substituent effect is carried out. [Formula: see text] and[Formula: see text] are nearly 50% in the adsorption process. In the surface reaction, the entropie contribution is greater (72.5%) than the enthalpic (27.5%).

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Thermodynamics of Ionization of Benzoic Acid and Substituted Benzoic Acids in Relation to the Hammett Equation

Canadian Journal of Chemistry ◽

10.1139/v74-423 ◽

1974 ◽

Vol 52 (16) ◽

pp. 2906-2911 ◽

Cited By ~ 46

Author(s):

Takeki Matsui ◽

Hon Chung Ko ◽

Loren G. Hepler

Keyword(s):

Benzoic Acid ◽

Ionization Constants ◽

Benzoic Acids ◽

Hammett Equation ◽

Good Linear ◽

Calorimetric Measurements ◽

Linear Relationships ◽

Best Value ◽

Substituted Benzoic Acids ◽

Thermodynamics Of Ionization

We have made both ampoule and titration calorimetric measurements leading to ΔH0 of ionization of aqueous benzoic acid at 298 K, and have considered our results in relation to those from several earlier investigations in an effort to select the "best" value for this important quantity. We have also made calorimetric measurements leading to ΔH0 values for ionization of several substituted benzoic acids, and have selected "best" ΔH0 values for 15 meta- and para-substituted benzoic acids. It is found that there are good linear relationships between ΔG0, ΔH0, and ΔS0 values for most of these substituted benzoic acids. It is also found that the Hammett equation accounts well for ionization constants over the temperature range 278–318 K for all of these acids and accounts very well for ionization constants of those acids with positive σ substituent parameters.

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Kinetics and Mechanism of Decomposition of 1,3-Bis(4-methylphenyl)triazene Catalyzed with Substituted Benzoic Acids in 25% Aqueous Methanol-General or Specific Catalysis?

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19942029 ◽

1994 ◽

Vol 59 (9) ◽

pp. 2029-2041

Author(s):

Oldřich Pytela ◽

Taťjana Nevěčná

Keyword(s):

Benzoic Acids ◽

Hammett Equation ◽

Aqueous Methanol ◽

Mechanism Of Decomposition ◽

Kinetics Of Decomposition ◽

Independent Variable ◽

Amino Derivatives ◽

Substituted Benzoic Acids ◽

The Individual ◽

Kinetics Of

The kinetics of decomposition of 1,3-bis(4-methylphenyl)triazene catalyzed with 13 substituted benzoic acids of various concentrations have been measured in 25 vol.% aqueous methanol at 25.0 °C. The rate constants observed (297 data) have be used as values of independent variable in a series of models of the catalyzed decomposition. For the catalytic particles were considered the undissociated acid, its conjugated base, and the proton in both the specific and general catalyses. Some models presumed formation of reactive or nonreactive complexes of the individual reactants. The substituent effect is described by the Hammett equation. The statistically best model in which the observed rate constant is a superposition of a term describing the dependence on proton concentration and a term describing the dependence on the product of concentrations of proton and conjugated base is valid with the presumption of complete proton transfer from the catalyst acid to substrate, which has been proved. The behaviour of 4-dimethylamino, 4-amino, and 3-amino derivatives is anomalous (lower catalytic activity as compared with benzoic acid). This supports the presumed participation of conjugated base in the title process.

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Mixed-dimer formation in binary systems of 4-substituted benzoic acids and structure considerations

Canadian Journal of Chemistry ◽

10.1139/v08-008 ◽

2008 ◽

Vol 86 (6) ◽

pp. 525-532 ◽

Cited By ~ 6

Author(s):

Maren Roman ◽

Annett Kaeding-Koppers ◽

Peter Zugenmaier

Keyword(s):

Benzoic Acid ◽

Crystalline Phase ◽

Liquid Crystalline ◽

Binary Systems ◽

Benzoic Acids ◽

Dimer Formation ◽

Crystalline Phases ◽

Cholesteric Phase ◽

Liquid Crystalline Phases ◽

Substituted Benzoic Acids

The phase behavior of binary systems of 4-substituted benzoic acids is governed by the formation of mixed dimers. This study was conducted to determine the effect of the components’ structural difference on mixed-dimer formation in crystalline and liquid-crystalline phases. The phase diagrams of two systems, with 4-[(S)-(–)-2-methylbutoxy]benzoic acid (MBOBA) as one component and 4-(hex-5-enoxy)benzoic acid (HOBA) and 4-(dec-9-enoxy)benzoic acid (DOBA), respectively, as the second component, were determined by differential scanning calorimetry, polarized-light microscopy, and X-ray diffraction. The MBOBA-HOBA system exhibited a cholesteric phase, two solid solutions, and above 58 °C for compositions between 40 and 80 mol% HOBA a crystalline phase of mixed dimers. The MBOBA-DOBA system showed a crystalline phase of mixed dimers at all compositions, a cholesteric phase, and a twisted smectic C phase, which was dominated by mixed dimers at 60 and 70 mol% DOBA. We conclude that liquid-crystalline phases are generally dominated by mixed dimers, but in crystalline phases the formation of mixed dimers is promoted by a greater difference in molecular structure. The crystal structure of two of the pure compounds MBOBA and DOBA and comparable compounds have been determined for an evaluation of the arrangements of the molecules in the crystal and liquid-crystalline state.Key words: benzoic acid, crystal arrangement, phase diagrams, liquid crystal.

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Analysis of the Gas Phase Acidity of Substituted Benzoic Acids Using Density Functional Concepts

Molecules ◽

10.3390/molecules25071631 ◽

2020 ◽

Vol 25 (7) ◽

pp. 1631

Author(s):

Jorge A. Amador-Balderas ◽

Michael-Adán Martínez-Sánchez ◽

Ramsés E. Ramírez ◽

Francisco Méndez ◽

Francisco J. Meléndez

Keyword(s):

Gas Phase ◽

Density Functional ◽

Chemical Potential ◽

Fukui Function ◽

Ortho Position ◽

Benzoic Acids ◽

Functional Theory ◽

Resonance Effects ◽

Gas Phase Acidity ◽

Substituted Benzoic Acids

A theoretical study of the effect of the substituent Z on the gas phase acidity of substituted benzoic acids ZC6H4COOH in terms of density functional theory descriptors (chemical potential, softness and Fukui function) is presented. The calculated gas phase ΔacidG° values obtained were close to the experimental ones reported in the literature. The good relationship between the ΔacidG° values and the electronegativity of ZC6H4COOH and its fragments, suggested a better importance of the inductive than polarizability contributions. The balance of inductive and resonance contributions of the substituent in the acidity of substituted benzoic acids showed that the highest inductive and resonance effects were for the -SO2CF3 and -NH2 substituents in the para- and ortho-position, respectively. The Fukui function confirmed that the electron-releasing substituent attached to the phenyl ring of benzoic acid decreased the acidity in the trend ortho > meta > para, and the electron-withdrawing substituent increased the acidity in the trend ortho < meta < para.

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